Bayesian Optimal Design Research Articles

Clinical update related to the first-in-human trial of SYS6002 (CRB-701), a next-generation nectin-4 targeting antibody drug conjugate.

3151 Background: SYS6002 (CRB-701) is a novel, nectin-4 targeting antibody drug conjugate (ADC) that take advantage of a third generation, site-specific cleavable linker with novel conjugation chemistry. This technology is designed to establish a stable linker across antibody and payload, to produce an ADC with a homogenous drug antibody ratio of 2.0, with the additional aim to reduce the concentration of free-MMAE and thereby improve known payload related toxicities. SYS6002 (CRB-701) also contains a novel monoclonal antibody with a prolonged half-life that can support Q3W dosing. Methods: This is a multicenter, open-label, single-arm, phase I study using Bayesian optimal interval design. Eligible patients were aged ≥18 years with histologically confirmed Nectin-4 positive solid tumors (no Nectin-4 testing was required for urothelial carcinoma [UC]) who had failed or were intolerant to standard of care options. In the dose escalation, patients were given SYS6002 (dose level 0.2, 0.6, 1.2, 1.8, 2.7, 3.6, and 4.5 mg/kg) administered Q3W by intravenous infusion. The primary endpoints were safety, tolerability, and the recommended phase 2 dose. Results: As of January 2024, SYS6002 (CRB-701) has established a differentiated safety profile across a broad dose range (0.2-3.6 mg/kg) with no dose limiting toxicities and the majority of adverse events representing grade 1 or 2. No low-grade peripheral neuropathy, skin rash or fatigue, known toxicities that rate limit the usage of enfortumab vedotin (EV) have occurred. Herein, we report the anti-tumor activity of SYS6002 (CRB-701) in patients with nectin-4 positive solid tumors with a median of 4 prior therapies. The first confirmed stable disease was observed at 0.6 mg/kg and the first confirmed partial response was at 1.2 mg/kg. Anti-tumor activity in nectin-4 positive patients at doses ≥ 2.7 mg/kg ( n=6) would suggest an overall unconfirmed objective response rate of 50%, and among them, the ORR of patients with UC was 50% (1/2), and that of patients with cervical cancer reached 67% (2/3). Across this group of patients, 4/6 had moderate to high nectin-4 expression (H-score ≥ 150) and 3 achieved a partial response, suggesting SYS6002 (CRB-701) could achieve a highly differentiated ORR of 75% in patients with moderate to high Nectin-4 expression. After single IV infusion of SYS6002 0.2-3.6 mg/kg, the exposure of TAb, ADC and MMAE generally increased in a dose proportional manner. The half-lives of TAb, ADC and MMAE were 4-6 days, 4-5 days and 5-10 days, respectively. SYS6002 (CRB-701) exhibited a longer ADC half-life and lower free-MMAE exposures relative to EV at comparable dose levels. Conclusions: SYS6002 (CRB-701) demonstrates promising anti-tumor activity with a well-tolerated safety profile in patients with advanced nectin-4 positive solid tumors. Dose escalation at 4.5 mg/kg Q3W and dose expansion at 3.6 mg/kg Q3W are ongoing. Clinical trial information: ChiCTR2200066256.

First-in-human study of RLY-2608, a pan-mutant and isoform selective PI3Kα inhibitor, as a single agent in patients (pts) with advanced solid tumors and in combination with fulvestrant in pts with advanced breast cancer.

TPS1128 Background: Oncogenic mutations in PIK3CA occur in ~35% of HR+, HER2– breast cancer (BC) and are frequent in multiple solid tumors. The approval of alpelisib, a non-mutant selective PI3Kα inhibitor, validates PI3Kα as a therapeutic target. However, inhibition of wild-type PI3Kα leads to significant toxicity, including hyperglycemia and rash. RLY-2608, a novel, oral allosteric PI3Kα inhibitor, is designed to overcome these limitations via mutant- and isoform-selective PI3Kα inhibition for greater target coverage, improved tolerability, and anti-tumor activity. ReDiscover (NCT05216432) is the ongoing, first-in-human study to investigate the maximum tolerated dose (MTD), recommended phase 2 doses (RP2Ds), safety, pharmacokinetics (PK), pharmacodynamics (PD) and anti-tumor activity of RLY-2608 monotherapy in pts with PIK3CA-mutant advanced solid tumors; and of RLY-2608 plus fulvestrant with or without ribociclib in pts with PIK3CA-mutant, HR+, HER2– BC. To date RLY-2608 plus fulvestrant has completed dose escalation; 400 and 600 mg BID is being investigated in the combination regimens, based on safety, PK, PD, and anti-tumor activity. Methods: This global, multi-center, dose escalation/expansion study of RLY-2608 monotherapy includes adult pts with advanced solid tumors who are refractory or intolerant to, or have declined, standard therapy. RLY-2608 is also being investigated in combination with fulvestrant and in combination with fulvestrant and ribociclib, each in previously treated pts with HR+, HER2– advanced/metastatic BC. Eligibility criteria include presence of a PIK3CA mutation (blood or tumor) per local assessment, ECOG performance status 0–1, evaluable disease per RECIST 1.1, and no prior treatment with a PI3K pathway inhibitor. RLY-2608 is administered daily in 4-week cycles. Adverse events (AEs) per CTCAE v5, PK, biomarkers (pAKT, mutant ctDNA and insulin pathway markers) and anti-tumor activity are assessed serially. Dose escalation employs a Bayesian Optimal Interval design to identify the MTD. Following dose escalation, expansion cohorts are enrolling patients with select PIK3CA-mutated solid tumors for treatment with RLY-2608 monotherapy and patients with HR+, HER2– metastatic BC for treatment with RLY-2608 plus fulvestrant with or without ribociclib. Primary endpoints are MTD/RP2D and AE profile; key secondary endpoints are PIK3CA genotype in blood and tumor, PK, biomarkers, and overall response rate. All dose expansion cohorts in ReDiscover are now enrolling in the United States and Europe. Clinical trial information: NCT05216432 .

Phase I clinical trial of peposertib plus radiation in adults with newly diagnosed MGMT-unmethylated glioblastoma.

2076 Background: DNA-dependent protein kinase (DNA-PK) is a pivotal component of DNA damage repair (DDR) pathways and is an attractive target in glioblastoma because its expression renders tumors less vulnerable to radiotherapy. Peposertib is a small molecule DNA-PK inhibitor that has been pre-clinically shown to potentiate radiotherapy and regress glioblastoma tumors. We conducted a two-stage phase I trial of peposertib plus radiation in patients with newly-diagnosed MGMT-unmethylated glioblastoma (NCT04555577). Methods: In stage 1, patients received concurrent peposertib plus standard-of-care radiotherapy to determine the maximum-tolerated dose (MTD) based on the Bayesian Optimal Interval design (maximum n=24). Stage 2 is a window-of-opportunity expansion cohort and will include 5 surgical patients to evaluate intratumoral drug concentration. Both groups receive 6 cycles of adjuvant temozolomide. Results: Eighteen patients completed the 10-week dose-limiting toxicity (DLT) period; 3@50mg, 3@100mg, 3@200mg, 9@300mg. One DLT (G3 radiation necrosis [RN] at 300mg) was observed. Enrollment of the last three patients into the 300mg dose level began in December 2023 and will complete stage 1. To date, most notable toxicity was transient G3 dermatitis of the scalp (2@200mg, 1@300mg; not a DLT per protocol). Therefore, radiation dose constraints to the skin were incorporated and subsequent patients did not experience this toxicity. After a median follow up of 14.3 months (9.3-18.4), the median OS was 22.9 months [95% CI (16-NR)] and median PFS was 12.7 months [95% CI (9-NR)]. Next-generation sequencing (NGS) was available for 16 archival tumor tissue specimens from patients treated on this trial. Two patients had pathology-proven RN (one within and one outside of the DLT period). Both tumors had baseline mutations in DDR genes (i.e. ATRX, DICER1). Recurrent tissue was available for 4 patients after treatment with peposertib, 2 of which demonstrated gain of DDR gene mutations (2 ATM mutations in one patient and gain of MAD2L2 mutation in another patient). Conclusions: The initial safety data of peposertib plus radiation in patients with newly-diagnosed MGMT unmethylated glioblastoma is favorable. The cases with RN in tumors with DDR mutations, the gain of DDR mutations in recurrent tumors, and the cases of scalp dermatitis suggest peposertib activity may correlate with DDR function, and possibly potentiates the effect of radiation. Stage I is an independent stage of the protocol that will enable MTD determination. Complete safety and survival data and correlations with genomics and spatial transcriptomics for Stage I patients will be presented at the meeting. The study was supported by EMD Serono (CrossRef Funder ID: 10.13039/100004755). Clinical trial information: NCT04555577 .

A phase 1a/b, multi-regional, first-in-human study of CS5001, a novel anti-ROR1 ADC, in patients with advanced solid tumors and lymphomas.

3023 Background: Receptor tyrosine kinase-like orphan receptor 1 (ROR1) is an embryonic tyrosine kinase-like molecule implicated in multiple pathways promoting oncogenic signaling. ROR1 is overexpressed in a broad spectrum of solid tumors and hematological malignancies while notably absent in normal tissues. CS5001 is an antibody drug conjugate (ADC) composed of a human anti–ROR1 IgG1 monoclonal antibody which is site-specifically conjugated to a pyrrolobenzodiazepine dimer prodrug through a proprietary lysosomal cleavable β-glucuronide linker. Here, we report preliminary phase 1a results of CS5001 in patients (pts) with advanced solid tumors and lymphomas. Methods: This is a global, first-in-human, phase 1a/b study evaluating the safety, pharmacokinetics (PK), and anti-tumor activity of CS5001 in pts with advanced solid tumors and lymphomas. CS5001 was administered intravenously Q3W with a 42-day-DLT period. In phase 1a (dose escalation), pts who had progressed on or been intolerant to standard therapies were enrolled without baseline ROR1 expression testing; accelerated titration followed by Bayesian Optimal Interval design was employed; in parallel with dose escalation, additional pts were enrolled to selected dose levels deemed safe to further evaluate safety and efficacy. Results: As of 15 Jan 2024, 49 pts with lymphomas (n=17) and solid tumors (n=32) were treated across 8 dose levels (7 to 125 μg/kg). Median age was 57 years. Most (n=40, 81.6%) pts had received ≥3 lines of prior anti-tumor treatment. No DLT was observed and MTD was not reached. Treatment-related adverse events (TRAEs) occurred in 29 pts (59.2%); the most common TRAE was fatigue (n=8, 16.3%). Grade 3 TRAEs occurred in 7 pts (14.3%), with fatigue, gamma-glutamyltransferase increased and pneumonia being the most common (occurring in 2 pts [4.1%] each). No grade 4-5 TRAEs were reported. Drug exposure of CS5001 was proportional to dose in general, with an apparent half-life of about 5 days. The PK profile of CS5001 was similar to that of total antibody, indicating good stability of the ADC in the circulation. Among the 34 pts with post baseline tumor assessment (13 lymphomas and 21 solid tumors), objective responses were observed in pts at dose level 5 or above (n=23), including 2 complete responses (1 Hodgkin lymphoma [HL] and 1 diffuse large B-cell lymphoma) and 3 partial responses (2 HL and 1 pancreatic cancer). Stable diseases were observed in 3 pts (2 colorectal cancer and 1 renal cancer). Dose escalation is still ongoing, and more data will be available at the conference presentation. Conclusions: CS5001 was well tolerated with no DLT identified, PK characteristics were as expected, and encouraging antitumor activities were observed in various advanced solid tumors and lymphomas. Current data support continued evaluations for the recommended phase 2 dose and subsequent phase 1b dose expansion. Clinical trial information: NCT05279300 .

Evorpacept plus enfortumab vedotin in patients (Pts) with locally advanced or metastatic urothelial carcinoma (la/mUC): Phase 1a dose escalation results.

4575 Background: Maximizing antibody dependent cellular phagocytosis (ADCP) in the tumor microenvironment requires both the inhibition of the myeloid CD47/SIRPα checkpoint and activation of the macrophage’s FcyR by an anti-cancer specific antibody (Lakhani et al. Lancet Oncol 2021). Evorpacept (EVO) is a CD47 inhibitor with an inactivated Fc effector domain that blocks the CD47-SIRPα interaction. Enfortumab vedotin (EV) is a nectin-4-directed antibody drug conjugate (ADC) which engages the FcyR on the macrophage. We evaluated whether EVO plus EV would be safe, tolerable and active in pts with la/mUC. Methods: 20 pts with la/mUC who had received prior platinum-based chemotherapy and progressed during or after treatment with a PD-1/L1 inhibitor were administered study drug in this phase 1 study (NCT05524545). Dose escalation (DE) cohorts were administered intravenous (IV) EVO 20 mg/kg or 30 mg/kg Q2W plus standard EV 1.25 mg/kg IV on days 1, 8 and 15 of a 28-day cycle. The primary endpoint was first cycle dose limiting toxicity (DLT) using a Bayesian Optimal Interval design. Additional pts were enrolled in both dose levels as backfill cohorts to further characterize safety, PK, PD, and preliminary antitumor activity. Investigator response was based on RECIST v1.1, and data cut off was 18Jan(safety)/24Jan(efficacy) 2024. Results: Fourteen pts were administered EVO 20 mg/kg Q2W (DE n= 3; backfill n=11) and 6 pts EVO 30 mg/kg Q2W (DE n=6) plus standard EV. No DLTs were observed, and the maximum tolerated dose (MTD) of the combination was not reached. The maximum administered dose (MAD) of EVO was 30 mg/kg Q2W combined with EV. There were no treatment-related deaths on study. Treatment emergent adverse events (TEAEs) occurring in > 25% of subjects included fatigue, diarrhea, abnormal loss of weight, dysgeusia, decrease appetite, hyperglycemia, constipation, hypomagnesemia, lacrimation increased, nausea, peripheral sensory neuropathy, rash maculo-papular and urinary tract infection (UTI). There were 3 serious adverse events that were related to EVO plus EV (G3 UTI [1 pt]; G4 neutrophil count decreased and G3 UTI [1 pt]). Sixteen patients were response evaluable. The overall response rate (ORR) was 63% (1CR, 9PR). Accrual is ongoing and updated data will be provided at the time of presentation. Conclusions: This is the first study, to our knowledge, reporting data on the combination of a CD47 blocking agent in combination with an ADC in la/mUC. EVO plus EV is well tolerated at doses evaluated with no MTD reached and a MAD of 30 mg/kg Q2W. The combination shows early promising clinical activity compared to an ORR of 41% with EV alone in pts with la/mUC who had previously received platinum-based chemotherapy and a PD-1/L1 inhibitor (Powles et al. N Engl J Med 2021). Further investigation in this refractory population, including patients with prior EV exposure, is warranted. Clinical trial information: NCT05524545 .

First-in-human study of ABBV-706, a seizure-related homolog protein 6 (SEZ6)–targeting antibody-drug conjugate (ADC), in patients (pts) with advanced solid tumors.

3001 Background: SEZ6 is a transmembrane protein expressed in small cell lung cancer (SCLC) and other neuroendocrine neoplasms (NENs), and central nervous system (CNS) tumors. These malignancies have a high unmet need for novel effective therapies. ABBV-706 is an ADC targeting SEZ6 conjugated to a topoisomerase 1 inhibitor payload at a drug-to-antibody ratio of 6, and is highly efficacious in preclinical models of SCLC, NENs, and CNS tumors. Here, results from ABBV-706 monotherapy dose escalation (DE) are presented. Methods: Phase 1, open-label, multicenter, DE and dose-expansion study (NCT05599984) of ABBV-706 as monotherapy or in combination with budigalimab (a programmed cell death 1 inhibitor), carboplatin, or cisplatin. Primary objectives are to determine the safety, PK, preliminary efficacy, and recommended phase 2 dose of ABBV-706. Exploratory objectives are to assess SEZ6 expression retrospectively and its association with safety, PK, and efficacy. DE enrolled adults (≥18 yr) with relapsed/refractory SCLC, high-grade CNS tumors, and high-grade NENs, following the Bayesian optimal interval design. ABBV-706 was administered IV at 1.3–3.5 mg/kg doses Q3W in 21-d cycles. Results: As of data cutoff on Nov 15, 2023, 49 pts (SCLC: n=22 [45%]; CNS tumors: n=5 [10%]; NEN: n=22 [45%]) were enrolled and treated with ABBV-706 in DE and backfill cohorts. Median age was 64 yr (range 32–81) and median prior lines of therapy was 2.5 (range 1–6). 2 pts had a dose-limiting toxicity: 1 G4 leukopenia and neutropenia lasting >7 d at 3.0 mg/kg and 1 G4 thrombocytopenia at 3.5 mg/kg. TEAEs occurred in 45 (92%) pts, the most frequent being anemia (51%), fatigue (41%), neutropenia (31%), and leukopenia (31%). G≥3 TEAEs occurred in 28 (57%) pts and were mainly hematologic: neutropenia (29%), anemia (27%), and leukopenia (25%). No pneumonitis/interstitial lung disease was observed. Gastrointestinal TEAEs (all G1/2) were seen in 55% of pts, with the most common being nausea (27%) and vomiting (18%). There were no ABBV-706–related deaths. The maximum tolerated dose was 3 mg/kg IV Q3W. ABBV-706 ADC showed an approximate dose-proportional increase in exposure with an elimination half-life of approximately 7 d across doses. For 33 RECIST-evaluable pts, the confirmed (c) objective response rate was overall 21% (7 partial responses [PRs]); 40% (6/15) for SCLC and 6% (1/18) for NEN. The overall response (c and unconfirmed [u]) rate without confirmation was 45% (7 cPRs/8 uPRs); 73% (6 cPRs/5 uPRs) for SCLC, and 22% (1 cPR/3 uPRs) for NEN. 8 uPRs are pending confirmation and will be reported in the final presentation. The clinical benefit rate was 91% (7 PR, 23 stable disease). No activity was observed in 3/3 pts with high-grade gliomas. Conclusions: ABBV-706 demonstrated a manageable safety profile with promising efficacy in SCLC and NENs. Further evaluation of ABBV-706 is ongoing. Clinical trial information: NCT05599984 .

Phase 1 study of BDTX-1535, an oral 4th generation covalent EGFR inhibitor, in patients with recurrent glioblastoma: Preliminary dose escalation results.

2068 Background: Epidermal growth factor receptor ( EGFR) gene is the most frequently altered oncogenic driver in glioblastoma (GBM). In-frame deletion alterations (e.g., EGFRvIII) and missense mutations co-occur in the setting of EGFR gene amplification and are characterized as a hallmark of disease pathogenesis in GBM. BDTX-1535 is an oral, highly potent, brain penetrant, selective, irreversible 4th generation tyrosine kinase inhibitor that targets EGFR alterations in GBM and NSCLC. Preliminary results of the Phase 1 dose escalation study (NCT05256290) of patients with recurrent GBM (rGBM) are presented here. Methods: BDTX-1535-101 is a first-in-human study that enrolled patients with either rGBM harboring EGFR alterations following standard of care or patients with locally advanced or metastatic EGFR mutated NSCLC that progressed on prior EGFR TKIs. Using an adaptive Bayesian optimal interval design in the Phase 1 part, patients were enrolled at increasing dose cohorts and were treated daily for 21-day cycles until treatment discontinuation. The primary objective was to determine the BDTX-1535 recommended Phase 2 dose based on the overall safety, PK, pharmacodynamics, and preliminary antitumor activity. Results: Twenty-seven patients with rGBM were enrolled in the Phase 1 cohort that consisted of 54 patients in total including 27 patients with NSCLC. Patients were treated across seven dose levels (15mg – 400mg QD). The mean age of patients with rGBM was 58.7 years (range 41-85) with 96% of patients with previous temozolomide (TMZ) treatment and a median of 2 lines of prior therapy (range 1-4). The most common all-grade treatment-related AEs across all cohorts were rash (78%), diarrhea (41%), fatigue (15%), stomatitis (11%), decreased appetite (11%), nausea (11%) and paronychia (11%). Gr 3 TRAEs ≥ 10% included rash (19%) reported at 300 or 400 mg QD doses. Plasma exposure of BDTX-1535 increased dose proportionally and had a half-life of ~15h, supporting once daily dosing. The maximum tolerated dose (MTD) is 300 mg QD. Among 19 evaluable patients for response based on RANO criteria, 1 confirmed partial response was observed and 8 patients achieved stable disease. Five patients remained on BDTX-1535 with stable disease for an extended period (>5 months) who previously performed poorly on TMZ with short treatment duration, and 1 patient continues on BDTX-1535 after 16 months of treatment. Conclusions: BDTX-1535 was well-tolerated up to 300mg daily, which is the MTD, and promising preliminary clinical activity was observed in patients with rGBM after relapse on standard of care treatment. Given the inability to reconfirm EGFR status at the time of treatment with BDTX-1535 in this Phase 1 trial, further exploration of BDTX-1535 in a “window of opportunity” study is ongoing (NCT06072586). Clinical trial information: NCT05256290 .

PEMDA-HN, an open-label, phase II, randomized controlled study of danvatirsen plus pembrolizumab compared to pembrolizumab alone in first-line recurrent and/or metastatic head and neck squamous cell carcinoma (RM HNSCC).

TPS6113 Background: Signal transducer and activator of transcription 3 (STAT3) plays critical roles in promotion of an immune-suppressive tumor microenvironment and survival of tumor cells. Danvatirsen (DANVA) is a 16-nucleotide, generation 2.5 antisense oligonucleotide designed to down-regulate the expression of human STAT3 mRNA. Over 500 patients with hematologic malignancies or solid tumors have been exposed to DANVA monotherapy or in combination. A tolerable safety profile has been demonstrated for DANVA and toxicities are manageable. The SCORES study in recurrent and/or metastatic (RM) HNSCC patients, naïve to programmed cell death (ligand)1 (PD-(L)1) therapy, demonstrated that DANVA in combination with the PD-L1 inhibitory antibody durvalumab administered in the second line setting appeared to result in a higher objective response rate (ORR) (22.6% [12.3-36.2]) compared with the ORRs seen with durvalumab alone in prior studies (Cohen E. et al. Ann. Oncol., 2018). Several patients had complete responses (CR, 9.4%). The ORR was higher in patients with a PD-L1 tumor proportion score (TPS) ≥1 and ≥20, with increasing benefit noted with higher PD-L1 expression compared with historic anti-PD-(L)1 monotherapy data. The current study aims at evaluating the first-line combination of DANVA with pembrolizumab, an anti-PD-1 agent approved as first-line monotherapy for RM HNSCC in patients with PD-L1 positive disease. Methods: PEMDA-HN is a multicenter, open-label, randomized phase 2 study utilizing a Bayesian Optimal design (BOP2). Approximatively 81 RM HNSCC patients with a PD-L1 combined positive score (CPS) score ≥1 will be randomized in a 2:1 ratio stratified based on CPS<20 and CPS≥20 to receive either DANVA (3 mg/kg IV Days 1, 3, and 5 and then weekly starting on Day 8) and pembrolizumab (200 mg IV every 3 weeks) or pembrolizumab alone as a first line therapy for recurrent or metastatic disease. Eligible patients will receive study treatment until disease progression or discontinuation. The primary endpoint of the study is ORR by response evaluation criteria in solid tumors version 1.1 (RECIST 1.1) as assessed by the investigator. Key secondary objectives are safety, additional antitumor activity evaluation (CR rate, duration of response, disease control rate, progression-free and overall survival) and pharmacokinetics. Efficacy (e.g. ORR, CR rate) will be evaluated in all patients and in subsets of patients with CPS<20, CPS≥20 and CPS≥50. Exploratory endpoints include but are not limited to target engagement and biomarker evaluation. The study is being, or will be, conducted at US, South Korea and United-Kingdom study centers. Clinical trial information: NCT05814666 .

Bayesian Optimal Designs for Multi-Arm Multi-Stage Phase II Randomized Clinical Trials with Multiple Endpoints

There is a growing need to evaluate of multiple competing drugs in phase II trials where the number of patients is often limited, and simultaneous assessment of both efficacy and toxicity is crucial. To avoid the waste of research resources, it is indeed more efficient to screen multiple drugs at once in a platform phase II setting. We aim to adapt the Bayesian optimal phase II (BOP2) design to multi-arm trials for both uncontrolled and controlled settings. The binary efficacy and toxicity endpoints are modeled by a Dirichlet distribution as a vector of four outcomes. Posterior marginal distributions at each analysis are used to derive the monitoring threshold that varies during the trial. We control the family-wise Type I error rate for multiple comparison against a common reference value or a shared control. We conduct simulation studies under both uncontrolled and controlled settings to evaluate the operating characteristics of the proposed design. Our simulations demonstrate that the design exhibits better operating characteristics compared to a design using a constant threshold and is less sensitive to changes in accrual rate relative to what was planned. The design had promising operating characteristics and could be used in phase II oncology clinical trials for evaluating multiple drugs at a time.

Abstract PO3-19-10: Phase 1b study of EZH1/2 inhibitor valemetostat in combination with trastuzumab deruxtecan in subjects with HER2 low/ultra-low/null metastatic breast cancer

Abstract Background Low HER2-expressing breast cancers have traditionally been classified as HER2-negative and treated as TNBC or hormone receptor (HR)-positive. Trastuzumab deruxtecan (T-DXd), an antibody-drug conjugate, composed of an anti-HER2 antibody conjugated to topoisomerase I payload, is approved for clinical use in HER2-low (IHC 1+ or IHC 2+/ISH negative) metastatic breast cancer (MBC). In the DAISY study (NCT04132960), meaningful clinical response was observed with T-DXd in HER2 IHC 0 MBC. Valemetostat is an oral, selective dual inhibitor of enhancer of zeste homolog 1 and 2 (EZH1/2, methyltransferases that specifically methylate histone H3 lysine 27. It is currently approved for patients with relapsed or refractory adult T-cell leukemia/lymphoma in Japan. EZH2-mediated PP2A inactivation has been shown to confer resistance to HER2-targeted therapy. Additionally, valemetostat has been shown to upregulate Schlafen11 (SLFN11), a putative DNA/RNA helicase, that regulates the sensitivity to DNA damaging agents such as topoisomerase I inhibitors. Consequently, this study examines the safety and anti-tumor activity of valemetostat in combination with T-DXd in subjects with HER2 low/ultra-low/null MBC. Trial Design This is a single-arm, phase-1b study to evaluate the safety and clinical activity of T-DXd in combination with valemetostat in patients with HER2 low/ultra-low/null MBC. The dosing for T-DXd is 5.4 mg/kg Q3W administered intravenously as indicated for current clinical use. Valemetostat will be evaluated at three dose levels (100 mg, 150 mg, and 200 mg orally), with starting dose (level 1) at 100 mg QD. The dose-limiting toxicity (DLT) evaluation period will be the first 2 treatment cycles (42 days). Eligibility criteria Specific aims Statistical methods Approximately 12 evaluable patients will be enrolled for the dose-escalation portion based on the Bayesian optimal interval design with a target DLT rate of 25%. Patients enrolled in cohorts of 3. The expansion will be performed at the RDE using the 2-stage Bayesian optimal dose-expansion design. In the first stage, 13 evaluable patients (including those treated at the RDE in the dose-escalation part) will be enrolled. If < 5 patients respond in the first stage, the study will be stopped for futility. If ≥ 5 responses are observed, 13 additional evaluable patients will be enrolled. If 11 or more responses are observed among the total of 26 patients the treatment will be regarded as promising. This two-stage design yields 78% power under the alternative hypothesis of ORR=50% (null ORR = 30%) while controlling the one-sided type I error at 10%. Contact information for people with a specific interest in the trial sdamodaran@mdanderson.org (NCT05633979) Citation Format: Senthil Damodaran, Toshiaki Iwase, Angela Marx, Jie Willey, Funda Meric-Bernstam, Debu Tripathy, Carlos Barcenas, Jangsoon lee, Naoto Ueno. Phase 1b study of EZH1/2 inhibitor valemetostat in combination with trastuzumab deruxtecan in subjects with HER2 low/ultra-low/null 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 PO3-19-10.

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 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.

Abstract CT080: A phase I study of CPI-613 (devimistat) in combination with chemoradiation in patients with pancreatic ductal adenocarcinoma

Abstract Background: Local tumor progression is a cause of significant mortality and morbidity in patients (pts) with inoperable pancreatic ductal adenocarcinoma (PDAC). Effective approaches to achieve durable local control are urgently needed. Metabolic reprogramming and enhanced mitochondrial function are known contributors to chemo- and radio-resistance in PDAC. CPI-613, a lipoic acid analog that selectively inhibits components of the Krebs cycle in tumors, showed promising preclinical synergy in combination with gemcitabine and radiation (gem-RT). We initiated a phase I study (NCT05325281) to determine the maximum tolerated dose (MTD) of CPI-613 when used with gem-RT. Here, we present the results from the first cohort of this study. Methods: Adult pts with inoperable PDAC that, by institutional multidisciplinary review, were considered to benefit from definitive local control of the primary tumor were eligible for the study. CPI-613 was administered once weekly by intravenous infusion over ~ 2 hours at a starting dose of 500 mg/m2 and dose-escalated using a Bayesian optimal interval design. Gemcitabine was given once weekly at 400 mg/m2 and RT at 45-54 Gray (Gy) in 25-30 fractions. Results: By Jan 7, 2024, six pts were enrolled, and five completed the treatment and dose-limiting toxicity (DLT) period. Table 1 describes the characteristics of these five pts. As CPI-613 was not associated with any additional toxicities, specifically cytopenia(s), after the first two pts, the study protocol was amended to allow CPI-613 to be administered on weeks gemcitabine was held for cytopenia(s). The study, therefore, enrolled five pts in the first cohort. All pts received ≥ 16 weeks of systemic chemotherapy with at least stable disease per imaging prior to enrollment. None of the pts experienced DLTs. All treatment-related toxicities were expected from gem-RT, unrelated to CPI-613, and manageable. The trial is currently enrolling pts in the second cohort (CPI-613 dose of 1000 mg/m2). Conclusions: CPI-613 combined with gem-RT was safe and well tolerated at a dose of 500 mg/m2. Recruitment to the study is ongoing to determine the MTD of CPI-613 in combination with gem-RT. Table 1. Characteristic of Patients Sex Race Age ECOG Stage Prior chemotherapy Chemotherapy duration (weeks) M W 67 1 LA FFX 16 M W 64 1 LA GnP 35 M W 73 1 BR* GnP 16 M B 71 1 LA GnP 27 M W 80 1 Oligometastatic** GnP 18 * Medically inoperable ** Two lung metastases treated with stereotactic body radiation therapy (SBRT); BR: Borderline resectable; B: Black; FFX: FOLFIRINOX; GnP: Gemcitabine/Nab-paclitaxel; LA: Locally advanced. M: Male; W: White Citation Format: Mandana Kamgar, Husain Yar Khan, Amro Aboukameel, Sahar F. Bannoura, Brian Y. Chung, Aniko Szabo, Yiwei Li, Mohammed Najeeb Al Hallak, Philip A. Philip, Ben George, Kathleen K. Christians, Douglas B. Evans, Susan Tsai, Beth Erickson, John M. Goldberg, Asfar S. Azmi, William A. Hall. A phase I study of CPI-613 (devimistat) in combination with chemoradiation in patients with pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT080.

Abstract CT037: A phase I investigator-initiated trial of evorpacept (ALX148), lenalidomide and rituximab for patients with relapsed or refractory B-cell non-Hodgkin lymphoma

Abstract Introduction. We have recently demonstrated that pro-tumoral SIRPα+ macrophages may mediate resistance to lenalidomide and rituximab (R2) in patients (pts) with relapsed or refractory (RR) B-cell non-Hodgkin lymphoma (B-NHL). Evorpacept (ALX148) is a novel high-affinity CD47 blocker that abrogates the ‘do-not-eat-me signal’ provided to SIRPα+ macrophages. In a phase I trial including 33 pts with RR B-NHL it was well tolerated in combination with rituximab. We hypothesized that evorpacept and R2 will be synergistic, and the combination will be safe and effective for the treatment of pts with RR B-NHL. Methods. This single arm phase I study (NCT05025800) was conducted between 11/2021 and 9/2023 (data cut-off 12/2023). Adult pts with RR B-NHL who had received at least 2 prior lines of systemic therapy (1 in case of indolent B-NHL [iNHL]) were included. Evorpacept was administered intravenously (IV), in a 28-day cycle, for 12 cycles, at two dose levels (DL): 30 mg/Kg on day (D) 1 and D15 (DL1), or 60 mg/Kg on day 1 (DL2); rituximab IV was given weekly during cycle 1, and on D1 during cycles 2-6; lenalidomide was given orally on D1-21 during cycles 1-6. Dose limiting toxicity (DLT) was evaluated according to CTCAE v5 during cycle 1 and a Bayesian Optimal Interval design was used, with a target DLT rate of 0.3. Response was assessed according to Lugano 2014 criteria. Results. Twenty pts were included in the study. Median age was 61 (27-85), 10 (50%) were male, and 7 (35%) were non-white; 15 (75%) had follicular lymphoma, 3 (15%) marginal zone lymphoma, 1 (5%) mantle cell lymphoma, and 1 (5%) Richter Syndrome; 20 (100%) had previously received an anti-CD20 monoclonal antibody, 13 (72%) chemoimmunotherapy, and 15/18 (83%) iNHL pts had intermediate-high FLIPI. Three pts were treated at DL1, 17 at DL2, and no DLT was observed. The most common grade 3-4 adverse events included: neutropenia (55%), infections (30%), ALT increase (15%), AST increase (10%), skin rash (10%), and anemia (10%). Eight (40%) pts experienced a cycle delay, mainly due to grade (G) 1 AST/ALT elevation; 6 (30%) required a dose reduction for lenalidomide, none for evorpacept; 1 pt discontinued treatment after 1 cycle due to G3 lenalidomide-associated myocarditis. Sixteen (80%) pts achieved CR and best overall response rate was 90%. After a median follow-up of 16 months (95% CI, 12-20 months), 1-year PFS rate was 70% and 1-year OS rate was 90%. Conclusions. The combination of evorpacept and R2 is well tolerated in pts with RR B-NHL, with similar toxicity and promising anti-tumoral activity as compared to historical CR rates with R2 alone (34%). Bulk RNA sequencing and multiplex immunofluorescence are being performed on tissue biopsies collected before and during treatment, to characterize its effects on the tumor immune microenvironment. A phase 2 study investigating its efficacy in pts with previously untreated iNHL is now enrolling. Citation Format: Paolo Strati, Lei Feng, Dai Chihara, Jason Westin, Sairah Ahmed, Luis Fayad, Jared Henderson, Jeffrey Davidson, Elizabeth McChesney, Loretta Nastoupil, Sattva Neelapu, Christopher Flowers. A phase I investigator-initiated trial of evorpacept (ALX148), lenalidomide and rituximab for patients with relapsed or refractory B-cell non-Hodgkin lymphoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT037.

Abstract CT098: Phase I study of GQ1005, a new generation HER2-ADC, in patients with HER2-expressing and HER2 mutated advanced solid tumors

Abstract Background: GQ1005 is a new generation antibody-drug conjugate, targeting HER2-expressing tumor cells with Topoisomerase I inhibitors (DXd) as its payload via a stable and cleavable linker. In preclinical studies, GQ1005 demonstrated comparable antitumor activity compared to Enhertu in multiple tumor cell line xenograft models with no noticeable toxicity, indicating higher therapeutic index. GLP toxicity studies demonstrated that GQ1005 was well tolerated, with the highest non-severe toxic dose determined to be 60mg/kg. This report presents the preliminary findings of an ongoing phase I study, which aims to evaluate the safety, tolerability, pharmacokinetics, and antitumor activity of GQ1005 in patients with advanced solid tumors expressing HER2 or harboring HER2 mutations. Methods: GQ1005 was administrated intravenously every 3 weeks. An accelerated titration design was employed for the initial 2mg/kg dose, followed by Bayesian Optimal Interval Design for subsequent dose levels of 4, 6, 7.2, and 8.4 mg/kg. The primary objective of this study was to evaluate the safety, tolerability, and to determine the MTD or RP2D. Results: As of Oct. 13th, 2023, 46 (30 in dose-escalation and 16 in dose-expansion phase) subjects with HER2-expressing/mutated advanced solid tumors, predominantly in breast cancer (18), and lung cancer (18) , were enrolled into the study. Patients received a median of 3 (range, 1-11) prior lines of treatment, and 86.4% of pts previously received anti-HER2 therapies before. During dose escalation, No DLT was observed in all doses, MTD was not reached up to 8.4 mg/kg. Treatment-related adverse events (TRAEs) occurred in 44 (95.7%) subjects. The most common TRAEs were grade 1 or 2, including nausea (52.2%), vomiting (39.2%), aspartate aminotransferase (AST) increased (39.1%), alanine aminotransferase (ALT) increased (23.9%), anemia (23.9%), anorexia (21.7%), fatigue (19.6%), leukopenia (15.2%), infusion-related reactions (15.2%) , decreased lymphocyte count (15.2%) and dizziness (15.2%). Grade ≥3 TRAEs only occurred in 4 subjects (8.7%), including anemia, decreased lymphocyte count and γ-glutamyltransferase (GGT) increased. Interstitial lung disease was observed in 6 pts received highest dose level and most of them have recovered. No drug-related deaths. The pharmacokinetics analysis showed the concentration of GQ1005 and TAb generally peaked rapidly and declined in a roughly biphasic manner. Among 38 evaluable subjects, 1 pt achieved complete response, 18 cases achieved confirmed partial response, and 11 had stable disease, the objective response rate was 50% (19/38), the disease control rate was 78.9% (30/38) , and the 6-month PFS rate was 43.0% in all patients. Conclusions: GQ1005 demonstrated a promising antitumor activity in HER2-expressing/mutated advanced solid tumors patients previously heavily treated, and showed a good tolerance and manageable safety profile. The dose expansion study is on-going at 7.2 mg/kg to establish the RP2D in four cohorts. (NCT06154343; sponsored by GeneQuantum Healthcare (Suzhou) Co., Ltd.) Citation Format: Caicun Zhou, Bo Yang, Ting Deng, Biyun Wang, Jian Zhang, Yuping Sun, Linlin Wang, Hongwei Yang, Jingfen Wang, Wei Li, Qi Song, Yuchong Yang. Phase I study of GQ1005, a new generation HER2-ADC, in patients with HER2-expressing and HER2 mutated advanced solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT098.

Abstract CT084: A phase 1 study of LY4101174 (ETx-22), an antibody-drug conjugate targeting nectin-4, in patients with advanced or metastatic urothelial cancer and other solid tumors (trial in progress)

Abstract Background: Nectin-4 is a cell adhesion molecule expressed in multiple tumor types.1 Enfortumab vedotin (EV), an antibody-drug conjugate (ADC) comprising a fully humanized nectin-4 antibody conjugated to the microtubule inhibitor, monomethyl auristatin E (MMAE), is approved for the treatment of advanced urothelial cancer (UC). However, skin toxicity, peripheral neuropathy, and hyperglycemia are clinically significant toxicities with EV. LY4101174 (ETx-22) is a next-generation nectin-4 targeting ADC comprising a humanized IgG1 Fc-silent monoclonal antibody linked to the topoisomerase I inhibitor, exatecan, via a maleimide-ß-glucuronide poly-sarcosine linker with improved stability and a homogeneous drug-antibody ratio (DAR) of 8. Preclinically, LY4101174 has demonstrated robust in vivo efficacy in tumor models across a range of nectin-4 expression levels and in the nectin-4-MMAE ADC treated resistant tumor model.2 Methods: LOXO-ENC-23001 is a global, open-label, multi-center, first-in-human phase 1 study of LY4101174 in patients (pts) with advanced or metastatic solid tumors known to express nectin-4. LY4101174 will be administered intravenously and evaluated initially on either every 2 weeks or 3 weeks schedule. Eligible pts (≥18 years) must have good performance status (ECOG PS 0-1) with metastatic UC, head and neck squamous cell carcinoma, esophageal, pancreatic, prostate, non-small cell lung, cervical, ovarian, or triple-negative breast cancer, and must have received or not be a candidate for available standard therapies. The study will be conducted in 2 phases: phase 1a dose escalation/dose optimization and phase 1b dose expansion. Dose escalation will utilize a Bayesian optimal interval design. Additional pts will be allowed to backfill to previously cleared dose levels that demonstrate therapeutically relevant exposures or direct evidence of clinical activity. The dose-limiting toxicity evaluation period will be 21 or 28 days based on dosing schedules. Phase 1b dose expansion cohorts will enroll pts with selected tumor types: mUC with no prior EV treatment (cohort B1), mUC with prior EV treatment (cohort B2), and other selected non-UC tumors (cohort C). Primary objectives are to determine the recommended phase 2 dose (RP2D) and assess the safety of LY4101174. Key secondary objectives are to evaluate the pharmacokinetic profile, immunogenicity, and antitumor activity of LY4101174 per RECIST v1.1. Nectin-4 expression and other biomarker data will be generated and correlated with clinical activity. 1Challita-Eid PM et al. 2016 Cancer Res 76(10):3003-13. 2Azim H et al. 2023 Mol Cancer Ther 22(12_Suppl):B128. Citation Format: Jonathan Rosenberg, Renaud Sabatier, Armelle Viceneux, Thibault de La Motte Rouge, Stephane Champiat, Loic Lebellec, Philippe Barthélémy, Guru Sonpavde, Xin Gao, Scot Niglio, Tian Zhang, Craig Gedye, Matthew Galsky, Matthew Milowsky, Melissa Reimers, Andrew Weickhardt, Enrique Grande, Daniel E. Castellano, Mehmet Bilen, Amita Patnaik, Robert Zerbib, Minna Balbas, Xiaojian Xu, Kaitlyn Aptaker, Arjun V. Balar, Ahmad H. Awada. A phase 1 study of LY4101174 (ETx-22), an antibody-drug conjugate targeting nectin-4, in patients with advanced or metastatic urothelial cancer and other solid tumors (trial in progress) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT084.

Abstract CT068: Interim results of the ongoing phase 1-2 clinical trial of KVA12123, an engineered IgG1 targeting VISTA, as monotherapy and in combination with pembrolizumab in patients with advanced solid tumors

Abstract V-domain Ig Suppressor of T-cell Activation (VISTA), a promising immuno-oncology target, is primarily expressed by immunosuppressive myeloid cells that infiltrate solid tumors. VISTA may contribute to resistance to anti-PD-(L)1 and anti-CTLA-4 therapies and correlates with a poor prognosis. KVA12123 is a human IgG1 monoclonal antibody that specifically binds to VISTA at neutral and acidic pHs. It was designed to improve pharmacokinetic (PK) characteristics as well as reduce the risk of cytokine release syndrome (CRS). KVA12123 exhibited strong anti-tumor activity alone and in combination with anti-PD1 in preclinical studies. It demonstrated an excellent safety profile in non-human primates. The VISTA-101 clinical trial is a first-in-human, Phase 1/2, multicenter, open-label, safety, PK and pharmacodynamic (PD) evaluation of KVA12123, both as monotherapy and in combination with pembrolizumab, in adult patients with advanced solid tumors (NCT05708950). METHODS: The phase 1 of VISTA-101 is an accelerated Bayesian Optimal Interval Design consisting of two arms: Part A) KVA12123 monotherapy dose escalation from 3 mg to 1000 mg including 6 cohorts and Part B) KVA12123 dose escalation from 30 mg to 1000 mg in combination with 400 mg fixed dosing of pembrolizumab including 4 cohorts. The primary objectives are safety, tolerability and to define a recommended phase 2 dose. Safety, PK and receptor occupancy data were considered during dose escalation. VISTA-101 is also assessing PD and predictive biomarkers of response. Patient tumor response is evaluated by iRECIST. RESULTS: Forty-two patients have been enrolled in the dose escalation monotherapy arm of the study. KVA12123 was administered at doses ranging from 3 to 1000 mg every 2 weeks over a 6-week cycle. KVA12123 was well tolerated at all dose levels and no DLTs were observed. The most frequently observed adverse events were grade 1 or 2 transient infusion-related reactions. No evidence of CRS-associated cytokines were detected. PK analysis demonstrated greater than dose-proportional exposure consistent with target-mediated metabolism. A VISTA receptor occupancy assay demonstrated full target engagement at doses of 30 mg and above. PD analysis indicated a dose-dependent induction of pro-inflammatory myeloid derived cytokines and chemokines involved in immune cell activation and recruitment to the tumor microenvironment including CCL2, CCL3, CCL4 and CXCL10. Increases in nonclassical monocytes, NK cells, CD4+ and CD8+ T cells were also demonstrated, consistent with observations made in preclinical models and indicative of VISTA target engagement. Patient tumor response evaluations in the monotherapy arm will be reported. The study continues to evaluate KVA12123 both as a monotherapy and in combination with pembrolizumab to define the recommended phase 2 dose. Citation Format: Evan Y. Yu, Jason Henry, Manish R. Patel, Paul Swiecicki, Ida Micaily, Benjamin Garmezy, Kalyan Banda, Vinny Hayreh, Kurt Lustig, Yulia Ovechkina, Shawn P. Iadonato, Thierry Guillaudeux, Lee Rosen. Interim results of the ongoing phase 1-2 clinical trial of KVA12123, an engineered IgG1 targeting VISTA, as monotherapy and in combination with pembrolizumab in patients with advanced solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT068.

Abstract CT276: Liberty-201: Maintenance fluoropyrimidine (FP) and bevacizumab with or without anti-lymphocyte activation gene-3 (LAG-3) antibody LBL-007 plus anti-programmed cell death protein-1 (PD-1) antibody tislelizumab (TIS) for patients (pts) with metastatic or unresectable microsatellite stable (MSS)/mismatch repair proficient (pMMR) colorectal cancer (CRC)

Abstract Background: LBL-007 is a monoclonal antibody targeting LAG-3, a receptor expressed on immune cells that negatively regulates T-cell proliferation and effector T-cell function. LAG-3 is frequently co-expressed with PD-1 on tumor-infiltrating T cells, and dual inhibition of LAG-3/PD-1 synergistically prevents tumor growth in mouse models. CRC is the second-highest cancer-related cause of death worldwide; pts diagnosed with metastatic CRC have a 5-year survival rate of 14%. Immunotherapy (IO) has only demonstrated clinical benefit in pts with microsatellite instability-high/MMR-deficient CRC, which accounts for 5% of CRC pts; however, improved therapy options for patients with MSS CRC remain limited. The combination of anti-LAG-3 + anti-PD-1 IO is currently being tested in clinical trials in pts with MSS CRC. Methods: This is a phase 1b/2, randomized, open-label study (NCT05609370). Pts with unresectable or metastatic CRC with locally or centrally confirmed pMMR or MSS status and no disease progression after induction treatment in first-line therapy are eligible. A maximum of 36 pts will be enrolled in phase 1b (safety run-in) to determine the recommended phase 2 dose. All pts will receive intravenous dual IO (LBL-007 + TIS) in combination with maintenance backbone (FP + bevacizumab). The dose of LBL-007 will be escalated from 150 mg every 3 weeks (Q3W) to 600 mg Q3W/400 mg Q2W using a Bayesian optimal interval design with informative prior. In phase 2, ~130 pts will be enrolled in the programmed death-ligand 1 (PD-L1)-positive group (tumor area positivity [TAP] ≥1%) and 60 patients in the PD-L1-negative group (TAP <1%). Pts with a PD-L1-positive status will be randomized 2:1:2 to receive dual IO + maintenance backbone (Arm A), LBL-007 + maintenance backbone (Arm B), or maintenance backbone only (Arm C). Pts with a PD-L1-negative status will be randomized 1:1 to receive dual IO + maintenance backbone (Arm D) or maintenance backbone only (Arm E). Treatment will continue until disease progression or unacceptable toxicity. The primary endpoint is safety in phase 1b and investigator-assessed progression-free survival (PFS) per Response Evaluation Criteria in Solid Tumors (RECIST) v1.1 in phase 2. Secondary endpoints include overall survival, PFS2, overall response rate, duration of response, safety, pharmacokinetics, and immunogenicity. Exploratory endpoints include potential biomarkers (including but not limited to PD-L1 and LAG-3). Citation Format: Heinz-Josef Lenz, Ying Yuan, Vivian Li, Juan Zhang, Lubna Jamal, Xiao Lin, Fuxiang Zhu, John H. Strickler. Liberty-201: Maintenance fluoropyrimidine (FP) and bevacizumab with or without anti-lymphocyte activation gene-3 (LAG-3) antibody LBL-007 plus anti-programmed cell death protein-1 (PD-1) antibody tislelizumab (TIS) for patients (pts) with metastatic or unresectable microsatellite stable (MSS)/mismatch repair proficient (pMMR) colorectal cancer (CRC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT276.

Abstract CT082: Phase I study of autologous CD8+ and CD4+ transgenic T cells expressing high-affinity KRAS G12V mutation-specific T cell receptors (FH-A11KRASG12V-TCR) in patients with metastatic pancreatic, colorectal and non-small cell lung cancers with KRAS G12V mutations

Abstract Background: KRAS, the most common driver oncogene in human malignancies, has predictable mutations. 85% of RAS mutations occur at the Glycine (G) 12 position with G12V being amongst the most common. Cancers driven by mutant KRAS include pancreatic (PDAC), colorectal (CRC), and non-small cell lung (NSCLC) malignancies. The prognosis of patients with activating KRAS mutations remains poor. Preliminary anti-tumor activity has been observed in the clinic with T cell receptor (TCR) T cell therapies targeting KRAS mutations, but durable clinical benefit is lacking. Rationale: FH-A11KRASG12V-TCR is an autologous CD8+ and CD4+ transgenic T cell product expressing (1) an HLA-A11-restricted, high affinity KRASG12V mutation-specific T cell receptor (TCR) and (2) the wildtype CD8α/β coreceptor enabling CD4+ T cell recognition of KRAS G12V presented on an MHC class I allele mediating helper T cell activity and cytotoxicity. The TCR sequence is derived from the peripheral blood of a healthy HLA-A11+ adult based on a strong pre-clinical dataset. Methods: This is an ongoing, investigator-initiated, Phase 1, first-in-human, single-center, open-label dose escalation study of FH-A11KRASG12V-TCR. The aims are to evaluate the safety, tolerability, maximum tolerated dose (MTD), and preliminary anti-tumor activity of FH-A11KRASG12V-TCR in patients with advanced PDAC, CRC, and NSCLC who express the HLA-A11-restricted KRAS G12V mutation. Dose modification will be guided by the Bayesian Optimal Interval design (BOIN). Patients will initially be treated in cohorts of 3 at each dose level (DL). BOIN will be used to identify the recommended dose for subsequent patients. The planned target doses are 5 x 109 transgenic TCR T cells in DL 1 with dose escalation up to 15 x 109 transgenic TCR T cells in DL 3. This study enrolls patients who are 18 years or older, HLA-A*11:01-positive, with KRAS G12V mutated metastatic PDAC, CRC, or NSCLC. Patients must have progressed on or be intolerant of at least two lines of prior therapies including any targeted therapies indicated for their current malignancy. Patients undergo leukapheresis prior to treatment and receive lymphodepleting chemotherapy with either cyclophosphamide intravenously (IV) and fludarabine IV on days -6, -5, -4, and -3 or bendamustine IV on days -4 and -3. FHA11KRASG12V-TCR is administered IV on day 0. The dose-limiting toxicity observation period is 28 days. Patients may receive an additional FHA11KRASG12V-TCR IV infusion at the same or lower dose as soon as 28 days or up to 1 year after the first infusion. One patient enrolled to date and the study is actively recruiting (NCT06043713). Citation Format: Elena Gabriela Chiorean, Andrew Coveler, Rachael Safyan, Stacey Cohen, Sylvia Lee, Cecilia Yeung, Mary Redman, Thomas Schmitt, Aude Chapuis, Philip D. Greenberg. Phase I study of autologous CD8+ and CD4+ transgenic T cells expressing high-affinity KRAS G12V mutation-specific T cell receptors (FH-A11KRASG12V-TCR) in patients with metastatic pancreatic, colorectal and non-small cell lung cancers with KRAS G12V mutations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT082.