Recommended Phase 2 Dose Research Articles

A phase 1, open-label, dose escalation, and expansion study of CUE-102, a novel WT1-pHLA-IL2-Fc fusion protein, in patients with HLA-A*0201-positive disease and WT1-positive recurrent/metastatic cancers.

3553 Background: Immuno-STATs are modular fusion proteins designed for the selective activation of tumor antigen specific CD8+ T cells. CUE-102, the second Immuno-STAT in clinical trials, is composed of a human leukocyte antigen (HLA) complex, HLA-A*0201, a peptide epitope derived from the Wilms Tumor 1 (WT1) protein, and 4 molecules of reduced affinity human interleukin-2 (IL-2). In preclinical studies CUE-102 binds, activates and expands WT1-specific CD8+ T cells with the potential to enhance anti-tumor immunity in patients with WT1+ cancers. Here we present the results of the dose-finding portion (Part A) of the CUE-102-01 study. Methods: CUE-102-01 is a 2 part phase 1 study. HLA-A*02:01 positive patients with WT1+ advanced colorectal (CRC), gastric (GA) and gastroesophageal junction (GEJ), pancreatic (PDAC) or ovarian (OvCa) tumors refractory to standard therapies were eligible for participation. WT1 status is determined by IHC via central testing. CUE-102 monotherapy was administered intravenously every three weeks in doses ranging from 1 mg/kg to 8 mg/kg following 3+3 design rules with a Bayesian Logistic Regression Model overlay. Dose levels that exhibit an immune or tumor response may be expanded to further characterize activity and toxicity as allowed by safety rules. Results: Dose escalation was successfully completed in 28 patients with CRC (17), PDAC (6), GA/GEJ (3) and OvCa (2). No DLTs were observed. Three dose levels (2, 4 and 8 mg/kg) exhibited evidence of immune activity and were expanded up to 9 patients each for further evaluation. CUE-102 was well-tolerated with > 96% of treatment-related adverse events (TRAEs) grade ≤2. The most common TRAEs, were fatigue, infusion reactions, nausea and vomiting. There were no cases of CRS Grade ≥ 2. Preliminary PK data demonstrate dose dependent increases in exposure across the dose range assessed. Preliminary analysis of patient samples demonstrates selective expansion of WT1-specific CD8+ T cells. Stable disease of ≥ 6 weeks (range 6-36 weeks), as determined by RECIST 1.1, has been observed in 10 of 23 patients (DCR 43.5%). Conclusions: CUE-102 is a novel T cell engager that demonstrates acceptable tolerability, favorable PK, and supportive preliminary PD readouts. No DLTs or drug-related SAEs have been observed in doses up to 8 mg/kg as of the data cut-off. Adverse events have been manageable and consistent with the CUE-102 mechanism of action and underlying disease. Early signs of disease stabilization and anti-tumor activity in late-stage patients are encouraging. Part B is a dose expansion that further evaluates safety, PK/PD, recommended phase 2 dose (RP2D), antitumor efficacy and is currently enrolling patients. Clinical trial information: NCT05360680 .

Evaluation of a novel method to guide belantamab mafodotin dosing in multiple myeloma based on a patient-reported questionnaire.

7530 Background: Ocular adverse events (OAEs, best corrected visual acuity [BCVA] change from baseline and keratopathy) are common with belantamab mafodotin (belamaf; GSK2857916) and often necessitate an ophthalmic exam to guide dosing. Herein, we evaluate a novel approach for belamaf dose modifications in transplant ineligible patients (pts) with newly diagnosed MM, treated with an extended schedule of belamaf with lenalidomide and dexamethasone (Rd) in the BelaRd study. Methods: BelaRd (NCT04808037) is an ongoing, phase 1/2 study of 2 Parts. Part 1 established the recommended phase 2 dose (RP2D) of 1.9 mg/kg q8w, extended to q12w to account for OAEs. Part 2 assesses the safety/efficacy of RP2D in Groups A and B, of 15 pts each, and evaluates two sets of guidelines for OAE management. In Group A, dosing is determined by an ophthalmic exam performed by a certified ophthalmologist; in Group B it is determined by the pts’ responses in the Vision Related Anamnestic (VRA) tool and the presence of ≥Grade (Gr) 3 OAEs. VRA is a patient-reported questionnaire capturing ocular symptoms and their impact on activities of daily living (ADL). Herein, we present the OAEs and preliminary efficacy results after 205 ophthalmic and VRA assessments for all Part 2 pts (cut-off date 05/10/2023). Results: By the cut-off date, the median belamaf administrations and number of cycles reached were 3.0/3.0 and 8.0/7.0 for Groups A and B, respectively. The respective rates of Gr2 and ≥Gr3 BCVA change from baseline were 34.6%/24.2% and 6.4%/0.0%, while a meaningful BCVA decline (Snellen score <20/50) and ≥3 lines drop in the better-seeing eye was recorded in 11.0%/7.2% ophthalmological assessments; no ≥Gr3 keratopathy was observed. Among 110/94 VRA assessments, ocular symptoms and ADL impairment, manifesting for ≥50% of the time in the last 24 hours prior to belamaf administration (substantial time), were noted in 6.4%/10.6% and 3.6%/7.4%. Of note, VRA captured a “substantial time” response in 86% of assessments with ≥Gr3 OAEs. Finally, for the response-evaluable pts, at a median follow-up of 7.7 months, ORR was 93.3%/85.7% in Groups A and B (PR/VGPR/CR: 26.7%/53.3%/13.3%; 21.4%/64.3%/0.0%) and the median time to first response was ~ 1 month. Conclusions: The VRA tool was safe and effective in informing belamaf dose modifications. Future analyses will determine if VRA may effectively eliminate the need for an ophthalmic exam prior to belamaf dosing. Clinical trial information: NCT04808037 . [Table: see text]

Updated efficacy and safety results from the phase Ib/II study of surufatinib combined with camrelizumab and chemotherapy in patients with advanced colorectal cancer.

e15547 Background: Preclinical and clinical data have demonstrated the synergistic anti-tumor effects of surufatinib, a novel VEGFR1-3, FGFR and CSF-1R inhibitor, in combination with immune checkpoint inhibitors (ICIs)/chemotherapy. A phase Ib/II, open-label study (NCT04929652) was conducted to evaluate the efficacy and safety of surufatinib plus camrelizumab (anti-PD-1), irinotecan and GM-CSF as second-line treatment in advanced colorectal cancer (CRC). In the phase Ib part, this combination showed favorable safety and efficacy profile, which was presented at ASCO 2023 in poster format (#255). Here, we reported the updated results from the phase Ib and phase II dose escalation part together. Methods: In the phase Ib, pts with CRC received surufatinib at 250mg once daily (QD) as starting dose, in combination with fixed dose of camrelizumab (200 mg, d1), irinotecan (200 mg/m2, d1) and GM-CSF (5ug/kg, d2-d7), every 3 weeks (Q3W). It had been reported in phase Ib that surufatinib 300 mg QD was defined as the recommended phase 2 dose (RP2D). In phase II dose expansion part, a further 36 pts were treated with the same regimen. The primary endpoint of phase II was ORR as per RECIST 1.1. Secondary endpoints included PFS, DCR, OS and safety. Results: As of Jan 18, 2024, 30 CRC pts (median age 57) were enrolled in the study with 12 pts in the phase Ib part and 18 pts in the phase II part. 70% were male and 23% had ECOG PS 1. 24/30 (80%) pts were positive for KRAS, NRAS or BRAF mutations. Among the 30 efficacy evaluable pts, the ORR was 30.0% (95% CI 14.7–49.4; 9 PR) and DCR was 93.3% (95% CI 77.9–99.2; 28 PR+SD). Pts with RAS/BRAF mutations were more likely to achieve better responses (9 PR in 24 pts, ORR-37.5%). After a median follow-up time of 11.1 months, the median PFS was 6.34 months (95% CI 4.57-9.23) and median OS was not mature. The most common grade 1-2 treatment related adverse events (TRAEs) (≥35%) were diarrhea (70%), fatigue (40%), anemia (36.7%), proteinuria (36.7%) and nausea (36.7%). Eleven pts experienced at least one grade 3 or 4 TRAEs. Grade 3 or 4 TRAEs occurred in > 1 pt included diarrhea (n = 3, 10%) and neutrophil count decreased (n = 2, 6.7%). Conclusions: Surufatinib plus camrelizumab, irinotecan and GM-CSF demonstrated promising anti-tumor activity in pts with advanced CRC, with a manageable safety profile. Expansion enrollment is ongoing and updated information will be presented. Clinical trial information: NCT04929652 .

SB221: A proof-of-concept study to assess the combination of SON-1010 (IL12-FHAB) and atezolizumab in patients with platinum-resistant ovarian cancer.

TPS5629 Background: Recombinant interleukins (rIL) have had limited clinical success due to inefficient tumor targeting and short PK, requiring frequent dosing that leads to aberrant immunostimulation and toxicity. IL-12 potently activates T and NK cells to produce IFNγ and kill tumor cells, yet dosing strategies have failed to provide adequate therapeutic benefit in humans. We developed a novel platform that delivers immunomodulator(s) linked to a fully-human albumin binding (FHAB) domain (Cini, Front Immunol 2023). Single-chain native IL-12 genetically linked to the FHAB provides enhanced tumor targeting and retention through albumin binding to over-expressed FcRn, GP60, and SPARC in the tumor microenvironment (TME), with an improved PK profile, a dose-sparing effect that decreases the toxicity risk, and a broader therapeutic index. Tumor growth inhibition in an immunologically ‘cold’ B16-F10 mouse melanoma model showed the efficacy of IL12-FHAB compared with rIL-12, resulting in significant increases in activated NK, NKT, Th1, and cytotoxic CD8 T cells. SON-1010 is being studied clinically as monotherapy (study SB101) in advanced solid tumors and in healthy volunteers (study SB102) (Chawla, AACR 2023). Atezolizumab (Tecentriq), an anti-PD-L1 immune checkpoint inhibitor (ICI), has shown preliminary clinical activity in Phase 1 studies of patients with platinum-resistant ovarian cancer (PROC) (Liu, Gyn Onc 2019; Moroney, Clin Canc Res 2020). SON-1010 may ‘warm up’ the TME to improve ICI effectiveness in these immunologically-active tumors that have high levels of SPARC. Methods: Study SB221 is a Phase 1b/2a multicenter, dose-escalation and proof-of-concept study to assess the safety, tolerability, PK, PD, and efficacy of SON-1010 administered SC, either alone or in combination with a fixed dose of atezolizumab given IV (NCT05756907). The study is designed in Part 1 to rapidly establish the maximum tolerated dose (MTD) of the combination in patients with advanced solid tumors with up to 5 dose-escalation groups and to expand the dataset using patients with PROC to establish the Recommended Phase 2 Dose (RP2D). Once the likelihood of efficacy is shown in a Simon 2-stage design, this will be followed in Part 2 by an assessment of the potential for improved efficacy of the combination in patients with PROC over SON-1010 alone or the standard of care (SOC). The first dose-escalation cohorts have been enrolled and additional sites are being added to help with recruitment of patients with PROC. Combination of SON-1010 with an ICI offers a unique opportunity to use this extended PK version of IL-12 to augment the potential for tumor control in PROC, which represents a significant unmet medical need. Clinical trial information: NCT05756907 .

Cadonilimab with chemotherapy in HER2-negative gastric or gastroesophageal junction adenocarcinoma: the phase 1b/2 COMPASSION-04 trial.

Treatment with anti-programmed cell death protein 1 (PD-1) therapy and chemotherapy prolongs the survival of patients with unresectable advanced or metastatic gastric or gastroesophageal junction (GEJ) adenocarcinoma. The benefit from anti-PD-1 therapy is enriched in patients with programmed cell death 1 ligand 1 (PD-L1) combined positive score (CPS)-positive or CPS-high tumors compared with patients with PD-L1 CPS-negative or CPS-low tumors. In this phase 1b/2 study, we evaluated the efficacy and safety of cadonilimab, a bispecific antibody targeting PD-1 and cytotoxic T-lymphocyte antigen-4, plus chemotherapy as first-line treatment in patients with human epidermal growth factor receptor 2-negative unresectable advanced or metastatic gastric or GEJ adenocarcinoma. The primary endpoint was the recommended phase 2 dose (RP2D) for phase 1b and the objective response rate for phase 2. Secondary endpoints included disease control rate, duration of response, time to response, progression-free survival, overall survival (OS) and safety. The primary endpoint was met. No dose-limiting toxicities were observed during dose escalation in phase 1b; the recommended phase 2 dose was determined as 6 mg kg-1 every 2 weeks. The objective response rate was 52.1% (95% confidence interval (CI) = 41.6-62.5), consisting of complete and partial responses in 4.3% and 47.9% of patients, respectively. The median duration of response, progression-free survival and OS were 13.73 months (95% CI = 7.79-19.12), 8.18 months (95% CI = 6.67-10.48) and 17.48 months (95% CI = 12.35-26.55), respectively. The median OS in patients with a PD-L1 CPS ≥ 5 was 20.32 months (95% CI = 4.67-not estimable); in patients with a PD-L1 CPS < 1, the median OS reached 17.64 months (95% CI = 11.63-31.70). The most common treatment-related grade 3 or higher adverse events were decreased neutrophil count (19.1%), decreased platelet count (16.0%), anemia (12.8%) and decreased leukocyte count (8.5%). No new safety signal was identified. The current regimen showed promising clinical activity and manageable safety in patients with gastric or GEJ adenocarcinoma regardless of PD-L1 expression. Chinadrugtrials.org.cn registration: CTR20182027.

Abstract PO1-06-14: Preliminary results of a phase I dose escalation study of eribulin in combination with copanlisib in patients with metastatic triple negative breast cancer (TNBC)

Abstract Background: Aberrant PI3K pathway signaling is frequently observed in TNBC. Increasing evidence indicate that PI3K pathway activation maintains the stemness and chemoresistance of breast cancer stem cells (CSCs). PI3K inhibition sensitizes CSCs to chemotherapy. Eribulin (E), a non-taxane microtubule dynamics inhibitor, showed overall survival benefit in metastatic HER2 negative BC. Preclinically, the addition of copanlisib (C), a potent pan-class I PI3K inhibitor that is highly selective against α and δ PI3K isoforms, improved anti-tumor effect in both E-sensitive and resistant TNBC patient-derived xenograft models, irrespective of PIK3CA/PTEN alteration status. Here we report the preliminary data of the phase I dose escalation trial of E+C in patients with metastatic TNBC. Methods: This trial includes a phase I study to determine the dose limiting toxicity (DLT) and recommended phase 2 dose (RP2D) of E+C, followed by a randomized phase II study of E+C (at RP2D) versus E (stratified by tumor PIK3CA/PTEN mutation status) with progression-free survival (PFS) as the primary endpoint. Key eligibility included patients with: metastatic TNBC who progressed on ≤5 lines of chemotherapy, prior anthracycline/taxane chemotherapy (unless contraindicated), ECOG 0-1, adequate organ function and known tumor PIK3CA/PTEN/AKT mutation status. Key exclusions include: prior receipt of E or any PI3K/mTOR/AKT inhibitor, grade ≥2 neuropathy, presence of tumor AKT mutation, and uncontrolled diabetes, hypertension or congenital QT prolongation. A 3+3 design was used to determine the DLT and RP2D. Dose level 1 (DL1) started with E at 1.1 mg/m2 mg IV and C at 45 mg IV on days (D) 1/8 of 21-D cycle, with the potential to escalate to 2 additional dose levels – DL2: E 1.4 mg/m2 and C 45 mg on D 1/8; DL3: E 1.4 mg/m2 and C 60 mg on D 1/8. Results: Eight patients were enrolled in the phase I study and received at least 1 dose of E+C. The median age was 48.5 (range, 26-67) years. The majority of patients identified as White (additionally 2 Hispanic, 1 Black) and had an ECOG performance status of 1 (n=6, 75.0%). Tumor PIK3CA and PTEN alterations were each observed in 1 patient. Median number of cycles received were 2 (range, 1-5). All 8 patients had at least 1 treatment-related adverse event (TRAE). The most common TRAEs across all dose levels were: lymphopenia (n=5, 62.5%), neutropenia (n=5, 62.5%), hyperglycemia (n=4, 50.0%), anemia (n=4, 50.0%) and fatigue (n=4, 50.0%); most toxicities were grade (G) 1-2. G3 hyperglycemia and hypertension were observed in 1 patient each, were medically managed and did not lead to treatment interruption. 1 patient was diagnosed with pulmonary embolism, possibly attributed to study therapy and breast cancer. DLTs were reported in 2 of 2 patients treated at DL2 - 1 patient developed G3 rash responsive to oral corticosteroids, and 1 patient developed G3 acute kidney injury in the setting of hypovolemia and discontinued study therapy. No additional patients were enrolled in DL2. No DLTs were observed in all 6 patients treated at DL1. 1 patient treated at DL1 had possible G1 non-infectious pneumonitis that resolved spontaneously on short interval imaging. Stable disease was observed in 2 of 6 response-evaluable patients (33.3%). 1 patient achieved regression of cutaneous disease following 1 cycle of therapy as assessed by the treating investigator. DL1, E at 1.1 mg/m2 plus C at 45 mg IV, was determined to be the RP2D. Tumor tissue biomarker analysis is underway. Conclusion: These data indicate that E+C at DL1 is a well-tolerated regimen warranting further investigation. The study is actively enrolling patients to the phase II study. Clinical trial information: NCT04345913. Funding Source: National Cancer Institute. Citation Format: Nusayba Bagegni, Brittney Haas, Leslie Nehring, Jingqin Luo, Laura Kennedy, Meghna Trivedi, Manali Bhave, Rabih Said, Cynthia Ma. Preliminary results of a phase I dose escalation study of eribulin in combination with copanlisib in patients with metastatic triple negative breast cancer (TNBC) [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-06-14.

Abstract PS17-06: A phase I trial of the PI3K inhibitor (PI3Ki) copanlisib and fulvestrant in combination with continuous or intermittent abemaciclib in patients with estrogen receptor-positive (ER+), HER2-negative (HER2-) metastatic breast cancer

Abstract Background: Activation of the phosphoinositide 3-kinase (PI3K) pathway is a prominent resistance mechanism to endocrine therapy and CDK4/6 inhibition (CDK4/6i) in ER+, HER2- breast cancer. There is reciprocal crosstalk between PI3K and cell cycle regulatory pathways. Triplet therapy that targets ER, CDK4/6, and PI3K prevents or delays disease progression in preclinical models of ER+, HER2- breast cancer. However, the toxicities of triplet therapy hinder its clinical development. Copanlisib (COP) is an intravenous (IV) PI3Ki with potent activity against α and δ isoforms. Intermittent high-dose PI3Ki is expected to be less toxic and more effective than continuous daily dosing. We set out to determine the recommended phase 2 dose (RP2D) for the COP/Fulvestrant (FUL)/Abemaciclib (ABE) combination. Methods: Eligible patients (pts) included men or women with ER+, HER2- metastatic breast cancer (MBC), with no more than 1 prior chemotherapy in the metastatic setting, and no limits on prior endocrine or targeted therapy. Prior FUL, CDK4/6i and PI3K/mTORi were allowed. Pts with HbA1c &amp;gt;8.5% were excluded. Pts received FUL 500 mg IM standard dosing and COP/ABE at assigned doses. Premenopausal women also received a GnRH agonist. Dose-limiting toxicity (DLT) was assessed during the first 28-day cycle. Adverse events (AEs) were graded according to NCI-CTCAE v5.0. Dose escalation/de-escalation was based on continual reassessment (CRM) and the RP2D was defined as the dose with the highest probability of the DLT rate within the acceptable 25~35%. Results: Between June 2020 and June 2023, 24 pts with ER+, HER2- MBC were enrolled. Table 1 shows the dose levels (DLs) and DLTs. The first 10 pts were enrolled to Part A on two consecutive DLs of COP (DL1: 45 mg IV D1 and D15, n=7; DL2: 45 mg IV D1, D8, and D15, n=3), with ABE fixed at 100 mg PO BID continuously. DL2a exceeded the maximum tolerated dose (MTD). DL1a was tolerable based on Cycle 1 AEs. However, during subsequent cycles, only 1 of the 7 pts in DL1a maintained the intended dose of ABE due to neutropenia, others reduced ABE to 50mg bid (n=5) or discontinued (n=1). This triggered a protocol amendment, adding Part B with ABE administered 5 days on and 2 days off (5-on/2-off) intermittent schedule. 14 pts were enrolled to Part B in 2 consecutive DLs of COP (DL1b: n=7; DL2b: n=7), the same as in Part A. ABE was fixed at 100 mg PO Bid 5-on/2-off. DL2b exceeded the MTD. DL1b was tolerable based on Cycle 1 AEs. In addition, in subsequent cycles, only 1 of 7 pts on DL1b required dose reduction of ABE to 50mg bid. RP2D is therefore defined as DL1b. Grade (G) 4 AEs were rare. The most common all cycle G3 AEs included transient hypertension (45%), rash (30%), anemia (25%), neutropenia (25%), and AST elevation (20%). As of 6/14/2023, 22 pts, with a median of 1 prior metastatic regimen (range 0-5), prior CDK4/6i in 18 (82%), liver mets in 8 (36%), and PIK3CA mutation in 8 (50%) of 16 pts with known mutation status, were evaluable for response. There were 5 partial responses and 3 stable diseases lasting for ≥24 weeks. Clinical benefit rate was 36.4% (8/22, 95%CI: 17.19% ~ 59.34%). Responses were observed in pts regardless of prior CDK4/6i, FUL, or PIK3CA mutation. Conclusion: COP/FUL/intermittent ABE can be safely administered with fair overall tolerability. Preliminary anti-tumor activity was observed, which will be further examined in the randomized phase II trial (NCT 03939897). Table 1 Dose-limiting Toxicities by Dose Level Citation Format: Cynthia Ma, Jingqin Luo, Jessica Moss, Maryann Kwa, Ritesh Parajuli, Katia Khoury, Emily Douglas, Ashley Frith, Caron Rigden, Foluso Ademuyiwa, Shana Thomas, Brittney Haas, Gerburg Wulf, Claire Dees, Rabih Said. A phase I trial of the PI3K inhibitor (PI3Ki) copanlisib and fulvestrant in combination with continuous or intermittent abemaciclib in patients with estrogen receptor-positive (ER+), HER2-negative (HER2-) metastatic breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PS17-06.

Abstract PO1-20-04: STX-478-101: A phase 1/2, first-in-human study of STX-478 monotherapy or in combination with fulvestrant in patients with breast cancer or other advanced solid tumors (trial in progress)

Abstract Background: The phosphoinositide 3-kinase-alpha (PI3Kα)/AKT/mTOR pathway is one of the major pathways in oncogenesis. PI3Kα alterations are especially prevalent in breast, gynecological, and head and neck squamous cell carcinomas. PI3Kα oncogenic mutations are highly enriched for kinase (H1047X) and helical (E542K, E545K) domain hotspots. The therapeutic potential of isoform-selective PI3Kα inhibition in PI3Kα-mutant cancers was established with alpelisib, which shows equipotent activity against both wild-type (WT) and mutant PI3Kα. However, alpelisib use is limited by toxicities induced by WT PI3Kα inhibition, e.g. hyperglycemia and mucositis. This suggests that mutant-selective PI3Kα inhibitors have the potential to improve efficacy while sparing WT-related toxicity. STX-478 is an investigational allosteric, mutant-selective PI3Kα inhibitor. Preclinical testing in human breast cancer xenografts bearing helical- or kinase-domain mutant PI3Kα demonstrated that STX-478 monotherapy and combinations with fulvestrant and/or CDK4/6 inhibitors provided robust efficacy without the metabolic dysfunction observed with alpelisib. Trial Design: This first-in-human, multicenter, phase 1/2 study (NCT05768139) evaluates the optimal dosing, safety, and preliminary efficacy of STX-478 as monotherapy in patients with locally-advanced or metastatic HR+/HER2− breast cancer or other solid tumor types with PI3Kα H1047X mutations, other kinase domain mutations, or helical domain mutations (Part 1), and STX-478 in combination with fulvestrant in patients with locally-advanced or metastatic HR+/HER2− breast cancer with PI3Kα H1047X or other kinase domain mutations (Part 2). Part 1 comprises 2 subparts (Table 1) to define the optimally biologically active dose (OBD) and maximum tolerated dose (MTD) in Part 1.1, and recommended phase 2 dose (RP2D) of STX-478 monotherapy in Part 1.2. At the conclusion of each dose-level in Part 1.1 (3 + 3 design), a backfill cohort will be initiated in patients with HR+/HER2− breast cancer with PI3Kα H1047X mutations or other kinase domain mutations, who will receive STX-478 at the determined safe dose. Part 2 comprises two subparts (Table 2) to define RP2D and assess the initial efficacy of STX-478 in combination with fulvestrant in patients with HR+/HER2− breast cancer expressing PI3Kα H1047X or other kinase domain mutations. Key Eligibility Criteria: Adults with a PI3Kα-mutant advanced or refractory solid tumor malignancy that is metastatic or locally advanced and unresectable, ECOG performance status score of 0–1, and no prior PI3K/AKT/mTOR inhibitor(s) use (except with prior intolerance) are eligible. Individuals with diabetes mellitus type 1 or uncontrolled diabetes mellitus type 2 are excluded. Cohort-specific eligibility criteria are provided in Tables 1 and 2. Endpoints: Efficacy, safety, pharmacokinetics, pharmacodynamics, patient-reported quality of life, and biomarkers (e.g., glucose metabolism, circulating tumor DNA) will be assessed. Trial Status: Recruitment opened April 2023 in the US and is ongoing, with potential for ex-US site expansion. Contact clinicaltrials@scorpiontx.com for additional information. Table 1. Part 1 Dose Escalation, RP2D Selection, and RP2D Expansion (STX-478 Monotherapy) Table 2. Part 2 RP2D Selection and Expansion (STX-478 + Fulvestrant Combination Therapy) Citation Format: Alberto Montero, Douglas Orr, Pamela Munster, Patricia LoRusso, Komal Jhaveri, Timothy Pluard, Ira Winer, Michael Streit, Monica Patterson, Simon Roberts, Stefani Corsi-Travali, Courtney Ewert, Dejan Juric. STX-478-101: A phase 1/2, first-in-human study of STX-478 monotherapy or in combination with fulvestrant in patients with breast cancer or other advanced solid tumors (trial in progress) [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-20-04.

Abstract PO2-05-01: Famitinib, a multi-targeted receptor tyrosine kinase inhibitor, combined with dalpicilib and fulvestrant in advanced HR-positive and HER2-negative breast cancer

Abstract Background: CDK4/6 inhibitors combined with endocrinotherapy (ET) represent an essential part of the treatment for HR-positive and HER2-negative breast cancer (BC). However, the role of angiogenesis inhibitors, such as bevacizumab, in these patients (pts) is controversial. While it has been demonstrated to improve progression-free survival (PFS), it has failed to show a significant overall survival (OS) benefit in HER2-negative BC. Several preclinical studies have explored the combination of anti-angiogenesis multi-targeted receptor tyrosine kinase inhibitors (TKIs) and CDK4/6 inhibitors in other cancers, suggesting a synergistic effect. Our phase Ib/II trial (NCT05176080, ChiCTR2100053950) aims to evaluate the safety and efficacy of a novel anti-angiogenesis TKI famitinib (F) added to dalpiciclib (D) and ET in advanced HR-positive and HER2-negative BC. Here we report the results of Phase Ib. Methods: A 3+3 de-escalation design was used in this dose-exploring phase (phase Ib). Pts with HR-positive and HER2-negative BC, who had no more than two prior chemotherapies in the advanced setting, were enrolled and administered F (orally, at doses of 15 mg/d, 10 mg/d, or 15 mg qod), D (orally, at doses of 150, 125 or 100 mg/d, 21 days on and 7 days off) and fulvestrant (intramuscularly, at a fixed dose of 500 mg every four weeks) until progression, unaccepted toxicities, or withdrawal. The initial dose level (Level 1) was set as F 15 mg daily and D 150 mg/d. The primary endpoints were recommended phase 2 dose (RP2D) and safety. Results: From December 2021 to June 2022, 18 pts were enrolled, and 3, 6, 3, and 6 pts were assigned to Level 1 (F 15 mg + D 150 mg), Level 2 (F 10 mg + D 125 mg), Level 3 (F 15 mg qod + D 125 mg), and Level 4 (F 10 mg + D 100 mg), respectively. 14 (77.8%) pts had visceral metastasis, and 7 (38.9%) had prior systemic therapies in the advanced setting. 13 (72.2%) pts had received ET, and 11 (61.1%) were resistant to ET before enrolled. A total of 6 dose-limiting toxicities (DLTs) were observed, including 3 Grade 4 thrombopenia (2 in Level 1, 1 in Level 2) and 3 Grade 4 neutropenia (2 in Level 3, 1 in Level 4), 4 of which were serious adverse events (AEs). The most common (≥20%) treatment-related AEs of Grade 3 or above were neutropenia (100.0%), leukopenia (88.9%), thrombocytopenia (33.3%), anemia (27.8%), lymphopenia and hypertension (both 22.2%). No death was reported. Overall 10 pts (55.6%) achieved confirmed partial responses and 16 (88.9%) achieved clinical benefits. Confirmed objective response rates (ORRs), clinical benefit rates (CBRs), and DLTs in different dose levels were shown in Table 1. Considering the efficacy and safety profiles, Level 4 was selected as RP2D. Conclusion: The anti-angiogenesis multi-targeted receptor TKI famitinib combined with CDK4/6i and fulvestrant has shown antitumor effects in advanced HR-positive and HER2-negative BC, and no new safety signals were observed. Citation Format: Min Yan, Mengwei Zhang, Limin Niu, Huimin Lv, Zhenzhen Liu, Huiai Zeng, Shengnan Zhao, Huihui Sun, Jing Wang, Yajing Feng, Huajun Li. Famitinib, a multi-targeted receptor tyrosine kinase inhibitor, combined with dalpicilib and fulvestrant in advanced HR-positive and HER2-negative breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-05-01.

Abstract PO3-20-04: A first-in-human study of the highly selective PI3Kα inhibitor RLY-5836 in patients with advanced breast cancer and other solid tumors

Abstract Background: Oncogenic activation of PI3Kα is a common driver event in solid tumors. Although PI3Kα is a validated therapeutic target, there is no approved highly selective inhibitor that targets mutant PI3Kα. Alpelisib, a non-selective orthosteric PI3Kα inhibitor, is approved in combination with fulvestrant for patients with PIK3CA-mutant, ER+, HER2– advanced breast cancer. Inhibition of wild-type PI3Kα causes hyperglycemia, limiting the tolerability, dosing, and efficacy of alpelisib. RLY-5836 is the second allosteric, selective pan-mutant PI3Kα inhibitor under clinical investigation. It is molecularly distinct with differentiated pharmaceutical properties compared to RLY-2608. This first-in-human study aims to further explore the tolerability and efficacy of highly selective PIK3CA-mutant inhibition as monotherapy and in combination treatment. Methods: This multicenter, open-label study is designed to evaluate the safety, maximum tolerated dose (MTD), recommended Phase 2 dose (RP2D), pharmacokinetics (PK) and preliminary anti-tumor efficacy of RLY-5836 as a single agent and in various combinations. A Bayesian Optimal Interval design is used for dose escalation, followed by a dose expansion part. As monotherapy, RLY-5836 will be investigated in pts with advanced solid tumors harboring a PIK3CA mutation (Arm 1) per local assessment (blood and/or tumor). In pts with PIK3CA-mutant, HR+, HER2– advanced or metastatic breast cancer, RLY-5836 combination arms will include anti-estrogen therapy with or without CDK4/6 inhibition: fulvestrant (Arm 2), and fulvestrant + CDK4/6 inhibitor(s) (Arms 3–5). RLY-5836 is administered orally, continuously in 28-day cycles until disease progression or study discontinuation. Enrollment criteria include age ≥18 years, ECOG PS 0–1, and measurable disease (Arm 1) or evaluable disease (Arms 2–5) per RECIST version 1.1. Participants in the combination arms are required to have received prior treatment with ≥1 CDK4/6 inhibitor and ≥1 anti-estrogen therapy. Prior treatment with a PI3Kα inhibitor is an exclusion criterion for the dose expansion parts of all arms. Planned overall sample size is ~220 pts (~145 pts for the dose escalation, and ~15 pts in each dose expansion arm). Primary endpoints are the MTD, RP2D and overall safety profile of RLY-5836, either as a single agent or in combination. The MTD will be determined as the dose with a dose-limiting toxicity rate closest to the target toxicity rate (30%) in Cycle 1. Secondary endpoints include PK and efficacy parameters. Statistical analyses will be descriptive. This study (NCT05759949) is enrolling in the United States. For further information, please contact clinicaltrials@relaytx.com. Funding source: This study is funded by Relay Therapeutics, Cambridge, MA, United States. Citation Format: Andreas Varkaris, Steven Isakoff, Cesar A. Perez, Bert O'Neil, Erika Hamilton, Erin Conlin, Gege Tan, Xiaoyan Li, Alison Timm, Ramin Samadani, Erika Puente-Poushnejad, Eunice Kwak, Brenton G. Mar, Alison M. Schram. A first-in-human study of the highly selective PI3Kα inhibitor RLY-5836 in patients with advanced breast cancer and other solid tumors [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-20-04.

Abstract PS15-01: A first-in-human phase 1 study of SIM0270, a brain-penetrant oral selective estrogen receptor degrader (SERD), in patients with ER+/HER2- locally advanced or metastatic breast cancer

Abstract Background: ER+/HER2- breast cancer is the most prevalent subtype, and endocrine-based therapy is the standard treatment. SIM0270 is a brain-penetrant and highly potent oral SERD that has demonstrated ER degradation and robust antitumor activity across various preclinical models, including those with intracranial xenograft tumors. Methods: This Phase 1 study evaluates the safety, pharmacokinetics and preliminary anti-tumor activity of SIM0270 as monotherapy and/or in combination with palbociclib or everolimus in patients with HR+/HER2- advanced or metastatic breast cancer. The primary objective of the phase 1a study, which consisted of the dose escalation stage and the dose expansion stage, is to determine the maximum tolerated dose (MTD) and/or recommended phase 2 dose (RP2D) of SIM0270 as monotherapy. A Bayesian Optimal Interval design (BOIN) was adopted. SIM0270 was administered orally daily in 28-day cycles. Here we report preliminary monotherapy data. Results: As of May 22nd 2023, 45 female patients were enrolled, receiving SIM0270 at dose levels of 10 mg (n=4), 30 mg (n=4), 60 mg (n=9), 90 mg (n=6), 120 mg (n=11), 200 mg (n=5), or 300 mg (n=6). The median age was 56 years (range, 40-73) and ECOG performance status was 0 (18%) or 1 (82%). Most patients were heavily pretreated, with a median of 2 prior endocrine-based therapies (range, 0-5) and a median of 2 prior chemotherapies (range, 0-8). Thirty-one patients (69%) received prior fulvestrant, 42 (93%) received prior aromatase inhibitors, and 28 (62%) received prior CDK4/6 inhibitors. Visceral metastases were present in 33 patients (72%), and brain metastases in 7 patients (16%). The most common TEAEs were sinus bradycardia (51%), anemia (38%), hypalbuminaemia (31%), hypercholesterolaemia (24%), urinary tract infection (24%), asthenia (24%), electrocardiogram (ECG) QT prolonged (24%), and dizziness (22%). Most of the TEAEs were Grade 1-2. Grade 3 TRAEs were ECG QT prolonged, gamma-glutamyltransferase(γ-GT) increased and dizziness in 2 patients each. All AEs were manageable with dose interruption or reduction, except only 1 patient discontinued treatment of SIM0270 due to TRAE (Grade 3 γ-GT increased). Four patients experienced dose-limiting toxicities (DLTs): 1 with Grade 3 ECG QT prolonged at 200mg dose level, 1 with Grade 3 ECG QT prolonged and 2 with Grade 3 dizziness at 300mg dose level. All DLTs were resolved with dose interruption then reduction. The MTD of single-agent SIM0270 was established as 200mg QD. Pharmacokinetic analysis revealed a T1/2 of approximately 70 hours, and the AUC and Cmax increased in an approximately linear manner with dose escalation. Concentration in cerebrospinal fluid was measured in 1 patient after 41 days treatment of SIM0270, which is consistent with preclinical data and suggested high concentration of SIM0270 in the brain of patients. Among 31 response evaluable patients (per RECIST 1.1 criteria), 4 PRs (3 unconfirmed) were observed, yielding an ORR of 12.9%. Brain lesions were all stable in 4 evaluable patients per RANO-BM criteria. In patients with ESR1 mutations at baseline and samples available for analysis, 4/6(67%) exhibited a reduction or loss of mutant ESR1 upon SIM0270 treatment. Conclusions: Single-agent SIM0270 was well tolerated and showed favorable antitumor activity in heavily pretreated advanced or metastatic ER+/HER2- breast cancer patients, including those previously treated with CDK4/6 inhibitors and fulvestrant. Phase 1a dose expansion with single-agent SIM0270 is ongoing, and the RP2D will be determined based on further accumulative data of tolerability and efficacy. (NCT05293964) Citation Format: Jiong Wu, Jian Zhang, Qingyuan Zhang, Yuping Sun, Hongtao Li, Yongmei Yin, Yehui Shi, Wenfeng Li, Yunjiang Liu, Min Yan, Chen Yang, Lili Zhu, Yang Yang, Liting Xue. A first-in-human phase 1 study of SIM0270, a brain-penetrant oral selective estrogen receptor degrader (SERD), in patients with ER+/HER2- locally advanced or metastatic breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PS15-01.

Abstract PO1-06-09: Phase 2 Trial with Safety Run-In of Gedatolisib Plus Talazoparib in Advanced Triple Negative or BRCA1/2 Positive, HER2 Negative Breast CancersBig Ten Cancer Research Consortium BTCRC-BRE18-337

Abstract Up to 2/3 of triple negative breast cancers (TNBC) have acquired defects in homologous recombination (HR) DNA repair, yet poly (ADP-ribose) polymerase inhibitor (PARPi) monotherapy has been largely ineffective in the absence of a germline BRCA 1/2 mutation (gBRCA1/2). Phosphoinositide-3-kinase (PI3K)/mTOR pathway alterations are also common in breast cancers. Preclinical data suggest that PI3K/mTOR inhibition may disrupt normal function of the HR complex and increase dependency on PARP enzymes for HR DNA repair. Thus, combining a PI3K/mTOR inhibitor with a PARPi may result in a synergistic anti-neoplastic effect. The run-in portion of this study evaluated the safety of weekly IV gedatolisib (PI3K/mTORi) and continuous daily talazoparib to determine the maximum tolerated dose (MTD) and recommended phase 2 dose (RP2D). A 3+3 design for dose escalation explored two dose levels. The phase II study began once the MTD and R2PD were confirmed. Eligibility required age ≥ 18, 1-2 prior lines of therapy (protocol later amended to allow up to 3 lines), and advanced TNBC or advanced HER2-negative BC with gBRCA1/2 mutation. The sample size for the phase II study was determined based on a 1-sided binomial test under the null and alternative ORR of 5% vs 20% with a type I error rate of 0.1 and power level of 80%. The primary endpoint was overall response rate (ORR) in TNBC without known gBRCA1/2 with secondary endpoints of progression-free survival (PFS) and overall survival (OS). Patients with a gBRCA1/2 mutation were not included in the primary endpoint analysis. Correlative studies are planned to evaluate HR deficiency mutations, PIK3CA mutations, and other exploratory genomics. A total of 33 patients were enrolled: 14 in the safety run-in phase of the trial and 19 in the phase II study (17 TNBC, 2 with gBRCA2 mutation). In the safety run-in, 6 patients were enrolled at dose level 1 (0.75 mg talazoparib po daily and 180 mg gedatolisib IV weekly) and 8 at dose level 2 (1 mg talazoparib po daily and 180 mg gedatolisib IV weekly). 42% of the cohort developed hyperglycemia, which was mostly grade 1. There was 1 DLT of grade 3 neutropenia at dose level 1. There were 3 patients who experienced grade 4 AEs, thrombocytopenia (2) and lymphopenia (1) which were outside of the DLT window. The MTD was 1 mg of talazoparib daily and 180 mg of gedatolisib weekly, and this was selected as the RP2D. A protocol amendment was made during the phase II portion to allow for a 3 week on/1 week off schedule for gedatolisib due to emerging data showing a more favorable safety profile and enhanced antitumor activity with this dosing schedule. In the 17 patients with TNBC and no gBRCA mutation in the phase II cohort, the ORR was 12%. Best response was partial response (PR) in 2 patients (12%), stable disease (SD) in 7 patients (41%), and progressive disease (PD) in 8 patients (47%). The clinical benefit rate (ORR+SD) at 16 weeks was 23.5%. The most common adverse events (AEs) in all 33 patients were anemia (70%), fatigue (67%), oral mucositis (64%), nausea (60%), neutropenia (45%) and anorexia (45%). Of these, most were grade 1-2 other than anemia (35% grade 3), neutropenia (20% grade 3), fatigue (18% grade 3), and oral mucositis (10% grade 3). There were no grade 4 AEs in the phase II study. Median PFS was approximately 3 months and median OS was approximately 6.4 months. Although this study did not meet its primary endpoint, there were 2 TNBC patients without a gBRCA1/2 mutation who achieved a partial response to this non-chemotherapy regimen. Future biomarker testing may help elucidate these findings and possible predictors of response. Citation Format: Sneha Phadke, Kari Wisinski, Oana Danciu, Ami Shah, Menggang Yu, Yi Chen, Kathy Miller, Mark Burkard. Phase 2 Trial with Safety Run-In of Gedatolisib Plus Talazoparib in Advanced Triple Negative or BRCA1/2 Positive, HER2 Negative Breast CancersBig Ten Cancer Research Consortium BTCRC-BRE18-337 [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-06-09.

Abstract PO5-05-03: Phase 1/2 Dose Expansion Study Evaluating First-In-Class eIF4A Inhibitor Zotatifin in Patients with ER+ Metastatic Breast Cancer

Abstract Background Zotatifin (eFT226) is a first-in-class, potent and sequence selective inhibitor of RNA helicase eIF4A that promotes a stable mRNA:eIF4A:drug ternary complex at specific polypurine motifs present within the 5’-UTR of select transcripts, thereby blocking production of the encoded proteins. In preclinical models zotatifin treatment simultaneously down-regulated translation of numerous oncogenes including CDK4, ERα, ERBB2, KRAS, and CCND1. Previous clinical research has demonstrated the activity of zotatifin in combination with other agents in ER+ metastatic breast cancer (MBC). Methods Part 1 is a 3+3 dose escalation portion of the protocol followed by Part 2 as a Simon’s two-stage design in patients with ER+ MBC enrolled at the recommended phase 2 dose (RP2D) of zotatifin (0.07 mg/kg IV two weeks on/one week off) in combination with fulvestrant (ful) and abemaciclib (abema) (Z+F+A). Part 1a and Part 1b are 3+3 dose escalation portions evaluating zotatifin in combination with ful (Z+F) at QW IV and Q2W IV dosing schedules, respectively. Key eligibility criteria included at least one line of therapy for advanced/metastatic disease, progression on hormone therapy, and in addition, the Z+F cohorts required prior CDK 4/6 inhibitor (CDKi). Primary endpoint of Part 1a/1b was determination of RP2D and primary endpoint of part 2 was objective response rate (ORR) per RECIST v1.1. Additional endpoints included safety, progression-free survival (PFS) and other efficacy analyses, and characterization of pharmacodynamic (PD) markers and pharmacokinetics. Results As of a data cut-off of July 6, 2023, 20 pts were enrolled in the Z+F+A cohort and had a median of four prior metastatic lines of therapy. In 19 evaluable pts in Z+F+A cohort, there were four confirmed partial responses (PR), one unconfirmed PR, and 10 pts with best overall response (OR) of stable disease (SD). All pts with PR/unconfirmed PR received prior CDKI, ful, and chemotherapy for MBC. Confirmed PRs were observed in patients with and without mutations in ESR1 and PIK3CA. mPFS, while not yet mature, exceeds 20 weeks. In Z+F+A the most common adverse events (AEs) were diarrhea (80%, all grades (Gr)) and nausea (75%, all Gr 1/2) and the most common Gr 3/4 AE was diarrhea (15%). In Z+F cohorts of 0.07 mg/kg QW (n=3), 0.1 mg/kg Q2W (n=3), and 0.14 Q2W (n= 2) there were no dose-limiting toxicities or Gr 5 adverse events (AEs). There was one confirmed PR and one SD in 0.1 and 0.14 mg/kg Q2W cohorts, respectively, and no PR or SD in the 0.07 mg/kg QW cohort. In Z+F+A, 9 pts had paired pre- and on-treatment ctDNA analyzed by Guardant assay. Of the remaining 11 pts, 4 came off study prior to scheduled collection of the on-treatment sample and 5 had unavailable samples. Of the 9 patients with paired samples, 8 had ctDNA decreases of &amp;gt;50%, all of whom had SD or PR. In the Z+F Q2W cohort, 2 of 3 patients had ctDNA decreases &amp;gt;50%, one of whom had a PR. Reduction below the limit of detection was seen for mutant alleles in ESR1, PIK3CA and other genes with potential to confer resistance to endocrine therapy. Conclusion Z+F+A showed encouraging efficacy in heavily pretreated ER+ MBC patients, with results that compare favorably to other treatment options available after progression on CDKi plus endocrine treatment. Efficacy was seen independent of ESR1 or PIK3CA mutations, suggesting the potential to treat a broad, unrestricted patient population. Initial results with Z+F Q2W dosing are encouraging and support continued dose escalation of this regimen. Citation Format: Ezra Y. Rosen, Manish Sharma, David Berz, Jennifer Caswell-Jin, Georgina Fulgar, Mark Densel, Gary Chiang, Samuel Sperry, Douglas Warner, Funda Meric-Bernstam. Phase 1/2 Dose Expansion Study Evaluating First-In-Class eIF4A Inhibitor Zotatifin in Patients with ER+ Metastatic Breast Cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-05-03.

Abstract PO4-18-07: A dose escalation and cohort expansion study of the CDK9 inhibitor KB-0742 in triple negative breast cancer and transcriptionally addicted relapsed or refractory solid tumors

Abstract Background: MYC deregulation is a hallmark of triple negative breast cancer (TNBC) and is associated with aggressive tumors and poor clinical outcomes. Although MYC remains undrugged, targeting of its cofactors has emerged as an attractive strategy to inhibit MYC oncogenic activity. Cyclin-dependent kinase 9 (CDK9) is a critical regulator of oncogenic MYC expression and an important MYC cofactor. KB-0742 is an oral CDK9 inhibitor that demonstrates promising preclinical activity against TNBC. In a real-world cohort, TNBCs have higher MYC expression and higher rates of MYC genomic amplification than other breast cancer subtypes. In primary patient-derived cell lines, KB-0742 treatment results in stronger cytotoxic effects in TNBC as compared to other subtypes. In patient-derived organoids and patient-derived xenografts, CDK9 inhibition by KB-0742 drives antiproliferative and anti-tumor growth effects, including in models that are resistant to standard of care. KB-0742 strongly downregulates MYC protein levels at doses that only partially inhibit CDK9 activity, suggesting a therapeutic window for tumor-specific activity (Saffran, D.C. et al, 2021). KB-0742 is currently being evaluated in a phase 1/2 dose escalation and cohort expansion study in patients with TNBC and other transcriptionally addicted tumors (NCT04718675). Trial design: This phase 1/2 study includes two parts: dose escalation (part 1) and cohort expansion (part 2). Part 2 includes cohort A (solid tumors with high prevalence of MYC overexpression including TNBC, non-small cell lung cancer and ovarian) and cohort B (other transcriptionally addicted tumor types including sarcomas, adenoid cystic carcinoma, nut midline carcinoma and small cell lung cancer). KB-0742 is dosed orally once daily for 3 consecutive days, followed by 4 days, off on a weekly basis in 28-day cycles until unacceptable toxicity or disease progression. Eligibility criteria: Part 1 dose escalation is open to patients with relapsed or refractory solid tumors. Part 2 is defined by tumor indications in cohorts A and B. Eligibly criteria include age &amp;gt; 18 years (≥ 12 years old and with a body weight ≥ 40 kg part 2 for cohort B), acceptable organ function, and ECOG PS &amp;lt; 2. Specific aims: Primary objectives include evaluation of pharmacokinetics (PK), pharmacodynamics (PD), safety, tolerability, preliminary anti-tumor activity, and identifying a maximum tolerated dose (MTD) and recommended phase 2 dose (RP2D). PK measurements include Cmax, tmax, AUC0-last, accumulation ratio (Racc) and t1/2. Safety data will be evaluated per the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE) v5.0. The Modified Continuous Reassessment Method (mCRM) (Goodman et al., Stat Med 1995) will guide dose escalation and MTD. RP2D nomination is informed by PD in peripheral blood mononuclear cells using assays to evaluate phosphorylation of the CDK9 substrate serine 2 on the RNA Polymerase II C-terminal domain (pSER2) and CDK9-responsive gene expression. Radiographic tumor response to KB-0742 in patients is assessed every other cycle starting from cycle two after treatment using RECIST 1.1 criteria. Target accrual: Targeted total enrollment is 170 patients. For additional information, contact clinicaltrials@kronosbio.com Citation Format: Monica Mita, Alain Mita, Miguel Villalona-Calero, Noah Federman, Drew Rasco, David Spigel, Jia Luo, Gregory Cote, Richard Cutler, Pavan Kumar, Crystal MacKenzie, Charles Lin, Jorge DiMartino, Elizabeth Olek, Brian Van Tine. A dose escalation and cohort expansion study of the CDK9 inhibitor KB-0742 in triple negative breast cancer and transcriptionally addicted relapsed or refractory solid tumors [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-18-07.

Abstract PO4-04-12: A Phase 1b/2 study of palazestrant (OP-1250) in combination with ribociclib or alpelisib in patients with estrogen receptor-positive, human epidermal growth factor receptor 2-negative, advanced and/or metastatic breast cancer

Abstract Background: Endocrine therapy (ET) when administered with cyclin-dependent kinase 4/6 (CDK4/6) inhibitors has improved outcomes in patients (pts) with estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer (BC) or metastatic breast cancer (MBC) and is the current standard of care for first-line treatment. Addition of the PIK3 inhibitor alpelisib to ET significantly improved progression-free survival in pts with PIK3CA-mutated, ER-positive, HER2-negative MBC, and alpelisib + fulvestrant is the standard of care for second or later-line treatment. Most pts will acquire resistance to ET, with mutations in ESR1 constituting the most common mechanism of resistance. Palazestrant (OP-1250) is a small molecule oral complete ER antagonist (CERAN) and selective ER degrader (SERD) that binds the ligand binding domain of ER and completely blocks ER-driven transcriptional activity in both wild-type (ESR1-wt) and mutant (ESR1-mut) forms of ER. In preclinical studies, palazestrant in combination with ribociclib demonstrated activity in both ESR1-wt and ESR1-mut xenograft models and showed efficacy in brain metastasis xenograft models. In a Phase 1/2 monotherapy study in pts with ER-positive, HER2-negative MBC, palazestrant was well tolerated with demonstrated antitumor efficacy and favorable pharmacokinetics (PK) supporting once a day (qd) dosing at the recommended Phase 2 dose (RP2D) of 120 mg. The aim of this study is to evaluate the safety, PK, and antitumor activity of palazestrant + ribociclib or alpelisib in pts with ER-positive, HER2-negative advanced BC or MBC. Methods: Eligible pts have evaluable ER-positive, HER2-negative advanced BC or MBC; ≤2 prior ETs (prior CDK4/6 inhibitors allowed); and ≤1 prior line of chemotherapy. In the alpelisib arm, pts must have a PIK3CA mutation in the tumor or ctDNA. Patients are administered oral palazestrant at escalating doses of 30, 60, and 120 mg qd in combination with the approved dose of oral ribociclib (600 mg qd; days 1–21 of 28-day cycle) or approved dose of oral alpelisib (300 mg qd) in a 3+3 design to identify the RP2D. The dose-expansion part will assess additional safety and PK parameters and the antitumor activity of palazestrant in combination with ribociclib or alpelisib (NCT05508906). Results: As of June 15, 2023, 10 pts have received 30 mg and 60 mg doses of palazestrant in combination with ribociclib (n=6) or alpelisib (n=4). No dose-limiting toxicities have been observed. After administration in the first two combination dose levels of 30 and 60 mg, palazestrant exposure was consistent with monotherapy administration; exposure data show no drug–drug interactions (DDI) when compared to published exposure parameters. Most reported treatment-emergent adverse events (TEAEs) were grade 1 or 2 and consistent with the known safety profiles of all 3 drugs. In the ribociclib arm, the TEAEs occurring in ≥2 pts included grade 1 nausea (n=4), grade 1 constipation (n=2), and neutropenia (grade 2, n=1; grade 3, n=3). For the 3 pts in the 30 mg palazestrant + alpelisib cohort, the only TEAE occurring in ≥2 pts was grade 1 diarrhea. One pt had grade 1 hyperglycemia. Conclusions: In this ongoing study, palazestrant in combination with ribociclib or alpelisib was well tolerated, and enrollment to the palazestrant 120 mg dose with ribociclib or alpelisib is ongoing. No new safety signals were observed for the 3 drugs, and no clinically significant DDIs were observed between palazestrant and ribociclib or alpelisib at the doses evaluated. Exposure of each drug was consistent with observed monotherapy exposure levels. Updated data will be presented. Citation Format: Virginia Borges, Carlos Alemany, Nancy Lin, Sara Nunnery, Cynthia Ma, Margaret Tonda, Morena Shaw, Arlene Chan. A Phase 1b/2 study of palazestrant (OP-1250) in combination with ribociclib or alpelisib in patients with estrogen receptor-positive, human epidermal growth factor receptor 2-negative, advanced and/or metastatic breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-04-12.

Abstract PO2-05-05: ELECTRA: An open-label, multicenter, phase 1b/2 study of elacestrant in combination with abemaciclib in patients with brain metastasis (mets) from estrogen receptor-positive (ER+), HER2-negative (HER2-) breast cancer (BC)

Abstract Background: Currently, there are no approved systemic treatment options specifically for patients with ER+/HER2- BC who have brain metastasis. The prevalence of brain metastases from ER+/HER2- BC is approximately 14% of women (Aversa, 2014). Elacestrant is a next-generation oral SERD that was evaluated in a pivotal phase 3 trial, EMERALD, as monotherapy vs. standard of care (SOC) endocrine therapy. The EMERALD trial reported significantly prolonged progression-free survival (PFS) with elacestrant vs SOC endocrine therapy in patients with ER+/HER2− ESR1 mutated (ESR1-mut) mBC following progression on prior endocrine therapy (Bidard, 2022). Elacestrant was well tolerated with a manageable safety profile. Most adverse events, including nausea, were low-grade and consistent with other endocrine therapies. A clinical study in healthy postmenopausal women demonstrated the ability of elacestrant to cross the blood-brain barrier (Conlan, 2020). Abemaciclib, a CDK4/6i, has been shown to achieve therapeutic concentrations in brain metastases tissue (Tolaney, 2020). Given the lack of current systemic treatments, elacestrant is now being evaluated with abemaciclib in patients with ER+/HER2- BC and brain metastasis (NCT05386108). Methods: ELECTRA (NCT05386108) is an open-label phase 1b/2, multicenter study evaluating elacestrant in combination with abemaciclib in patients with brain metastasis from ER+, HER2- BC. Eligibility are patients with ER+/HER2− locally advanced or mBC and measurable brain metastasis. For phase 1b, the presence of brain metastases is allowed but not required for eligibility. For phase 2, patients must have ≥ 1 active and measurable brain metastasis per RECIST v1.1. Patients must have received prior therapy in the metastatic setting, including ≥ 1 ET, ≤2 chemotherapy regimens, and 0-2 prior CDK4/6i (excluding abemaciclib). The primary objectives of Phase 1b are to determine the recommended Phase 2 dose (RP2D). Phase 1b secondary objectives include safety, PK, objective response rate (ORR), duration of response (DoR), clinical benefit rate (CBR), PFS, and overall survival (OS). Phase 2 primary objective is ORR per RECIST version 1.1. Phase 2 secondary objectives include intracranial response rate (RR), DoR, CBR, PFS, OS, PK, and quality of life (QoL). The phase 1b portion evaluated dose-limiting toxicities (DLTs) of the combination during the first cycle (28 days) of treatment in up to three 6-patient cohorts, starting at elacestrant 300 mg daily plus abemaciclib 100 mg twice daily. Here we report initial safety results from the phase 1b portion. Results: As of June 2023, 15 patients have been enrolled in the phase 1b portion of the trial. At dose level 1, elacestrant 300 mg QD + abemaciclib 100 mg BID, no patient experienced DLTs, and the combination was feasible. Dose level 2, elacestrant 400 mg QD + abemaciclib 100 mg BID has been completed, and no patients experienced DLTs. In dose level 1, 4/7 patients remain on treatment at cycle 5. Additional safety and PK data for the cohorts will be provided. Conclusion: In the phase 1b portion of ELECTRA, dose level 1 and dose level 2 have been completed. No patients experienced DLTs in either dose level 1 or dose level 2, and the combination was considered feasible in the respective dose levels. Dose level 3 (elacestrant 400 mg QD + abemaciclib 150 mg BID) is proceeding. Recruitment is actively ongoing, enabling oral-oral combinations to determine a RP2D. Citation Format: Nuhad Ibrahim, Sung-Bae Kim, Nancy Lin, Ahmad Awada, Eva Ciruelos Gil, Giulia Tonini, Bartomeu Piza Vallespir, Kathy Puvana Theall, Erika Hamilton. ELECTRA: An open-label, multicenter, phase 1b/2 study of elacestrant in combination with abemaciclib in patients with brain metastasis (mets) from estrogen receptor-positive (ER+), HER2-negative (HER2-) breast cancer (BC) [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-05-05.

Abstract PO4-27-05: A phase I open-label dose escalation trial of FWD1802 as monotherapy and in combination with palbociclib in patients with ER+/HER2- unresectable locally advanced or metastatic breast cancer with or without ESR1 mutations

Abstract Background: Estrogen receptor (ER) signaling sits at center of the tumor biology in ER+/HER2- breast cancers. Current standard of care involves hormone therapy with agents including selective estrogen receptor modulators (SERMs), selective estrogen receptor degraders (SERDs), and aromatase inhibitors (AIs). Unfortunately, most patients eventually develop resistance to these therapies. Mutations in estrogen receptor 1 (ESR1) are partially responsible for the acquired resistance. Mutated estrogen receptors are still sensitive to fulvestrant but with a much less sensitivity. In January 2023, elacestrant received its first approval for the treatment of postmenopausal women or adult men with breast cancer harboring ESR1 mutations in US. However, there is still great unmet medical need for this population. FWD1802 is a third-generation oral SERD for ER-positive breast cancer patients. It binds competitively to ER, with a much higher affinity than that of fulvestrant. Preclinically, FWD1802 alone and in combination with palbociclib exhibits significant anti-tumor activity in the ER+/HER2- models and in ESR1-mutated models in vitro and in vivo. This ongoing phase I study is to assess the safety, tolerability, pharmacokinetics (PK) and clinical activity of FWD1802 as monotherapy and in combination with palbociclib in ER+/HER2- unresectable locally advanced or metastatic breast cancer with or without ESR1 mutations. Methods: This clinical study (CTR20232130) consists of three parts: monotherapy dose escalation (Part A), dose escalation in combination with palbociclib (Part B) and monotherapy dose expansion in ESR1-mutated patients (Part C). A conventional “3+3” design is used for this study. Approximately a total of 129 patients will be enrolled. FWD1802 is administered orally daily. In monotherapy dose escalation study (Part A), at each dose level, a single ascending dose (SAD) is followed by a 28-day continuous multiple ascending dose (MAD) period (defined as 1 cycle). In Part B dose, palbociclib (125 mg daily) is administered on a 28-day treatment cycle with 21-day on treatment and 7-day off treatment, along with the 28-day treatment cycle of FWD1802. The primary objectives include dose limiting toxicity (DLT), maximum tolerated dose (MTD), safety, tolerability, and the recommended phase 2 dose (RP2D) of FWD1802. Secondary objectives include pharmacokinetics characteristics of FWD1802 and its major metabolite as monotherapy and in combination with palbociclib. Preliminary anti-tumor activity including objective response rate (ORR), duration of response (DoR), disease control rate (DCR) and progression-free survival (PFS) will also be evaluated. DLT evaluation will be conducted after the first cycle of multi-dose period, and tumor assessment will be conducted every 8 weeks by investigators according to RECIST version 1.1. Patients with ER+/HER2- unresectable locally advanced or metastatic breast cancer with or without ESR1 mutation are eligible for the enrollment. Enrolled patients should have progressed disease, or failed from previous therapy, or intolerable or inaccessible to standard therapy. In addition, patients with ECOG score ≤1 and with adequate renal, cardiac, hepatic, and hematologic function are eligible for enrollment. The monotherapy dose escalation (Part A) is currently ongoing. The dose selection for Part B and Part C will be based on the data from the ongoing Part A. Clinical trial information: CTR20232130. Research Sponsor: Shenzhen Forward Pharmaceuticals Co., Ltd. (FORWARD PHARMA). Citation Format: Ling Zeng, Jin Liu, Dan Wu, Huiwen Ge, Zirui Bian, Chenggang Zhu. A phase I open-label dose escalation trial of FWD1802 as monotherapy and in combination with palbociclib in patients with ER+/HER2- unresectable locally advanced or metastatic breast cancer with or without ESR1 mutations [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-27-05.

Abstract PO2-27-01: TFX06, a next-generation oral CERAN/SERD, shows favorable safety and PK profile, extracranial and intracranial efficacy in patients with ER+/HER2- breast cancer: Preliminary results from a phase 1/2 first-in-human trial

Abstract Aims: TFX06 is an investigational oral complete estrogen receptor (ER) antagonist (CERAN) and selective ER degrader (SERD) (Wu J, et al., 2023 AACR annual meeting). A Phase 1/2, multicenter, open-label dose-escalation and dose-expansion study (CTR20230789) was initiated in China to evaluate TFX06 in previously heavily treated patients with ER+/HER2- locally advanced and/or metastatic breast cancer. The primary objectives were to assess safety and tolerability, recommended Phase 2 dose (RP2D), and pharmacokinetics (PK). Methods: A 3+3 dose-escalation design was implemented. TFX06 tablets were orally administered at 60 mg/100 mg daily for 28 days of treatment cycle until disease progression or intolerant to TFX06. As of the cut-off date (Sept. 15, 2023), the Phase 1 study enrolled five patients with Stage IV diseases with distant metastases. Three were treated with TFX06 at 60 mg, the starting dose and two at the next dose level of 100 mg. Median age of patients were 50 years (39-65) with a ECOG score of 0-1. Two out of five patients carried estrogen receptor 1 (ESR1) mutations (ctDNA). Prior anticancer treatments included one or two lines of endocrine therapies, including fulvestrant, and/or one or two lines of chemotherapies. Clinical responses by investigator according to RECIST v1.1 were performed every two cycles to explore preliminary efficacy. Results: Three patients in 60 mg and one in 100 mg dose cohorts completed dose-limiting toxicity (DLT) observation period. No DLT observed. All treatment related adverse events (TRAEs) were grade 1-2 in severity, including nausea, drowsiness, decreases in WBC and neutrophils, and anemia. Analyses of plasma concentrations of TFX06 in all three patients receiving 60 mg revealed a similar PK profile with small variations in Cmax. The average steady-state Cmax and Cmin of TFX06 were 101 ng/mL and 65 ng/mL, respectively, and the Cmax of TFX06 was approximately 4-fold higher than that of fulvestrant administered intramuscularly at 500 mg in clinic (28 ng/mL). Two patients in the 60 mg cohort were evaluable for response assessment. One patient discontinued due to progressive disease (PD) after two cycles of treatment. This patient experienced a 17.1% decrease in target lesions in the lung; however, new metastases to bone observed. The other patient who carried ESR1 D538G mutation showed a decrease of 91% in ESR1 mutation burden 8 days after treatment, and a decrease of 34.2% in target lesions (partial response, PR), including a substantial shrinkage of 78.6% in the brain lesion (target lesion), as well as complete responses (CR) of non-target lesions in lung after 4 cycles of treatment. This patient remains on the study as of the cut-off date. Conclusions: Based on the preliminary results, oral administration of TFX06 at 60 or 100 mg once daily had favorable safety and PK profiles. TRAEs, such as gastrointestinal toxicities, bradycardia, and visual disturbances were not observed. Pleasingly, TFX06 demonstrated early extracranial and intracranial antitumor activity (PR) in a patient with a brain metastasis. Citation Format: Zhaojian Fu, Zhiye Zhang, Jia Song, Yang Chen, Douglas Fang, Wei Sha, Jian Zhang, Charles Ding. TFX06, a next-generation oral CERAN/SERD, shows favorable safety and PK profile, extracranial and intracranial efficacy in patients with ER+/HER2- breast cancer: Preliminary results from a phase 1/2 first-in-human trial [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-27-01.

Abstract PO3-20-03: First-in-human global study of RLY-2608, a pan-mutant and isoform selective PI3Kα inhibitor, as a single agent in patients with advanced solid tumors and in combination with fulvestrant in patients with advanced breast cancer

Abstract Background: Oncogenic mutations in PI3Kα are common driver events in ER+ breast cancer and other solid tumors. Alpelisib, a non-mutant selective PI3Kα inhibitor, is effective in ER+ breast cancer thus validating PI3Kα as a therapeutic target. Inhibition of wild-type PI3Kα results in toxicity including hyperglycemia which limits tolerability and drug exposure. RLY-2608, a novel, oral allosteric PI3Kα inhibitor, is uniquely designed to overcome these limitations via mutant- and isoform-selective PI3Kα inhibition for greater target coverage, improved tolerability, and antitumor activity. Initiated in December 2021, ReDiscover is the ongoing, first-in-human study to define the maximum tolerated dose (MTD), safety, pharmacokinetics (PK), pharmacodynamics (PD) and anti-tumor activity of RLY-2608 monotherapy in PIK3CA-mutant advanced solid tumor patients (pts) and of RLY-2608 plus fulvestrant in pts with PIK3CA-mutant, HR+HER2-BC. At AACR 2023, dose escalation data for RLY-2608 was reported and demonstrated encouraging target inhibition and anti-tumor activity (including partial response), across PIK3CA genotypes with minimal impact on glucose homeostasis. To date, pts have received RLY-2608 at doses of 100–2000 mg/day, with no reported dose-limiting toxicities; the MTD has not been reached. These proof-of-mechanism data indicate that RLY-2608 is the first allosteric, pan-mutant selective PI3Kα inhibitor and that RLY-2608 has broad therapeutic potential in PIK3CA-driven cancers. Methods: Enrollment is ongoing in this global, multi-center, dose escalation/expansion study of RLY-2608 as a single agent in adults who have advanced solid tumors and are refractory, intolerant, or have declined standard therapy; and RLY-2608 in combination with fulvestrant in previously treated pts with HR+/HER2– MBC. Eligibility criteria include presence of PIK3CA mutation (blood or tumor) per local assessment, ECOG performance status 0–1, evaluable disease per RECIST 1.1 and no prior PI3K inhibitor (except in expansion combination group 2). RLY-2608 is administered on a continuous schedule with 4-week cycles. Adverse events (AEs) per CTCAE v5, PK, biomarkers (pAKT, mutant ctDNAs and insulin pathway markers) and anti-tumor activity are assessed serially. Dose escalation employs a Bayesian Optimal Interval design to identify the MTD and/or the recommended Phase 2 dose (RP2D). Following dose escalation, expansion cohorts will enroll patients with select PIK3CA-mutated solid tumors for treatment with RLY-2608 monotherapy and patients with HR+/HER2– MBC for treatment with RLY-2608 and fulvestrant. The primary endpoints are MTD/RP2D and AE profile for single agent and combination; key secondary endpoints are PIK3CA genotype in blood and tumor, PK, biomarkers, and overall response rate. ReDiscover (NCT05216432) is enrolling worldwide. For further information, contact clinicaltrials@relaytx.com. Funding source: This study is funded by Relay Therapeutics, Cambridge, MA, United States. Citation Format: Andreas Varkaris, Komal Jhaveri, Elena Garralda Cabanas, Lucia Sanz, Janice Kim, Cesar A. Perez, Erika Hamilton, Alexander I. Spira, Kari Wisinski, Angel Guerrero, Jason Henry, Jordi Rodon Ahnert, Gege Tan, Xiaoyan Li, Diana Hummel, Tamieka Hunter, Alison Timm, Ramin Samadani, Erika Puente-Poushnejad, Eunice Kwak, Brenton G. Mar, Alison M. Schram. First-in-human global study of RLY-2608, a pan-mutant and isoform selective PI3Kα inhibitor, as a single agent in patients with advanced solid tumors and in combination with fulvestrant in patients with advanced breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-20-03.

Binimetinib in combination with nivolumab or nivolumab and ipilimumab in patients with previously treated microsatellite-stable metastatic colorectal cancer with RAS mutations in an open-label phase 1b/2 study

BackgroundIn patients with previously treated RAS-mutated microsatellite-stable (MSS) metastatic colorectal cancer (mCRC), a multicenter open-label phase 1b/2 trial was conducted to define the safety and efficacy of the MEK1/MEK2 inhibitor binimetinib in combination with the immune checkpoint inhibitor (ICI) nivolumab (anti–PD-1) or nivolumab and another ICI, ipilimumab (anti-CTLA4).MethodsIn phase 1b, participants were randomly assigned to Arm 1A (binimetinib 45 mg twice daily [BID] plus nivolumab 480 mg once every 4 weeks [Q4W]) or Arm 1B (binimetinib 45 mg BID plus nivolumab 480 mg Q4W and ipilimumab 1 mg/kg once every 8 weeks [Q8W]) to determine the maximum tolerable dose (MTD) and recommended phase 2 dose (RP2D) of binimetinib. The MTD/RP2D was defined as the highest dosage combination that did not cause medically unacceptable dose-limiting toxicities in more than 35% of treated participants in Cycle 1. During phase 2, participants were randomly assigned to Arm 2A (binimetinib MTD/RP2D plus nivolumab) or Arm 2B (binimetinib MTD/RP2D plus nivolumab and ipilimumab) to assess the safety and clinical activity of these combinations.ResultsIn phase 1b, 21 participants were randomized to Arm 1A or Arm 1B; during phase 2, 54 participants were randomized to Arm 2A or Arm 2B. The binimetinib MTD/RP2D was determined to be 45 mg BID. In phase 2, no participants receiving binimetinib plus nivolumab achieved a response. Of the 27 participants receiving binimetinib, nivolumab, and ipilimumab, the overall response rate was 7.4% (90% CI: 1.3, 21.5). Out of 75 participants overall, 74 (98.7%) reported treatment-related adverse events (AEs), of whom 17 (22.7%) reported treatment-related serious AEs.ConclusionsThe RP2D binimetinib regimen had a safety profile similar to previous binimetinib studies or nivolumab and ipilimumab combination studies. There was a lack of clinical benefit with either drug combination. Therefore, these data do not support further development of binimetinib in combination with nivolumab or nivolumab and ipilimumab in RAS-mutated MSS mCRC.Trial registrationNCT03271047 (09/01/2017).