Dose-limiting Toxicity Observation Period Research Articles

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.

TPS792 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 with T cell receptor (TCR) T cell therapies targeting KRAS mutations, but durable clinical benefit is lacking. FH-A11KRASG12V-TCR is an autologous CD8+ and CD4+ transgenic T cell product expressing (1) an HLA-A*11-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-A*11+ adult based on a strong pre-clinical dataset. Methods: This is an ongoing, investigator-initiated, phase 1, first-in-human, single-center, 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-A*11-restricted KRAS G12V mutation. Dose modification is guided by the Bayesian Optimal Interval design (BOIN). Patients are initially 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 10 9 transgenic TCR T cells in DL 1 with dose escalation up to 15 x 10 9 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 one line 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, and -4 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. The study is actively recruiting. Clinical trial information: NCT06043713 .

PBP1510, a novel monoclonal antibody targeting pancreatic adenocarcinoma upregulated factor (PAUF): Phase 1/2a monotherapy and combination with gemcitabine in patients with advanced/metastatic pancreatic cancer.

e16296 Background: PAUF, a protein overexpressed in pancreatic cancer but not in non-cancerous tissues, plays a key role in cancer progression and metastasis. PBP1510 is a novel first-in-class humanized IgG1 monoclonal antibody that binds to and neutralizes PAUF with high specificity and affinity. PAUF-I (NCT05141149) is a first-in-human, multicenter, open-label study in patients with advanced/metastatic pancreatic cancer. Early Phase 1 results are presented here. Methods: Key eligibility criteria for Phase 1 include: locally advanced/metastatic pancreatic cancer; at least 1 previous line of chemotherapy; ECOG 0-1; and measurable disease by RECIST v1.1. A 3+3 dose escalation design is planned for 5 dose levels of intravenous PBP1510 (doses of 1, 3, 6, 10, and 15 mg/kg), either alone (monotherapy cohorts) or in combination with gemcitabine at a dose of 1000 mg/m2 (combination cohorts), in 28-day cycles. Tumor assessments are performed every 8 weeks from the first dose of PBP1510. Dose is escalated following a safety review committee meeting, if all patients in a cohort complete the dose-limiting toxicity (DLT) observation period (28 days from first dose) without any DLTs. Primary endpoints are safety parameters including treatment emergent adverse events (TEAEs) and laboratory findings. Results: As of January 2024, 6 patients (4 males, 2 females), aged 54-71 years, were enrolled. All patients had stage IV ductal adenocarcinoma and had received at least 2 prior lines of chemotherapy. Five patients received 2 cycles of PBP1510 each at 1 mg/kg or 3 mg/kg based on their cohort. One patient received 1 cycle of PBP1510 at 3 mg/kg. Seventeen TEAEs were assessed to be related to study treatment. The most frequently reported treatment-related TEAE was asthenia (n = 7). Most treatment-related TEAEs were NCI-CTCAE Grade 1 in severity (n = 14). Five serious TEAEs not related to study treatment were reported in 2 patients. There was 1 death reported due to disease progression. No patient discontinued treatment due to TEAEs. No clinically significant abnormalities in ECG, LVEF, and clinical laboratory assessments were reported during the DLT observation period. All patients in the first 2 monotherapy cohorts completed the DLT observation period without any DLTs. Conclusions: PBP1510 was well tolerated by all patients at 1 mg/kg or 3 mg/kg in the first 2 monotherapy cohorts. The next monotherapy (PBP1510, 6 mg/kg) and combination (PBP1510, 1 mg/kg; gemcitabine 1000 mg/m2) cohorts are open for recruitment. Clinical trial information: NCT05141149 .

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.

Abstract CT035: Proof-of-concept and preliminary efficacy of triple IAP blockade to maximize immunogenic cell death and induce efficient adaptive immune response: First report on the ASTEROID phase 1 trial

Abstract Background: Dying cells play an important role in CD8+ T cell-mediated immunity. While apoptosis is mainly immunologically silent, necroptosis is immunogenic and can more efficiently initiate an adaptive immune response that could be augmented by immune checkpoint inhibition (ICI). Inhibitor of Apoptosis (IAP) proteins are key gatekeepers of how a cell dies, and frequently overexpressed in cancer. ASTX660 (tolinapant) is a triple blocker of cIAP1/2 and XIAP, sensitizing cancer cells to death ligands through ripoptosome formation, activating ‘danger’ co-stimulatory signals and dendritic cell (DC) maturation required to prime a potent antitumor response. Methods: We assessed the safety, pharmacodynamic (PD), and clinical activity of 7 days of oral ASTX660 given prior to pembrolizumab 200 mg (Q3W), in patients (pts) refractory to standard therapy. TITE-CRM was used to explore ASTX660 doses 90-180 mg. Serial paired blood and tumor samples were analyzed to interrogate the effect of ASTX660 on cell death, tumor microenvironment and host immune system. Results: 22 pts have been enrolled; median age 55 years (range 38-81); male:female 5:17; all ECOG PS ≤1; median 4.5 prior therapies. Tumor types included breast, head and neck (HN), hepatocellular, cervical, pancreatic and cholangiocarcinoma. Combination ASTX660-pembrolizumab is currently recruiting at highest dose 180 mg without any dose limiting toxicities (DLT) seen within the 6-week DLT observation period. Most common adverse events (AE) were G1-2 rash, nausea, and asymptomatic increases in amylase, lipase and transaminases; all reversible and easily manageable. Four iRECIST confirmed partial responses were seen in 10 efficacy evaluable pts treated at biologically active dose levels 120 and 150 mg (Overall response rate 40%), including 2 pts with ER+ HER2- breast cancer, 1 cervical adenocarcinoma pt (exceptional response following initial pseudoprogression) and a HN cancer pt refractory to ICI monotherapy. 3/4 responders are ongoing. Efficacy data from pts treated at highest dose level 180 mg is pending. FACS of paired blood samples from responders shows a significant rise in %CD57+/CD3+ cytotoxic effector T cells [mean 11.90% (pre-) vs 14.25% (post-ASTX660); p=.0176]. These changes were not seen in the non-responders group. Full PD from paired blood and tumour sampling will be shared at the meeting. Conclusion: ASTX660-pembrolizumab is is well-tolerated with durable antitumor responses in pts with immunologically cold tumors, providing the first clinical proof-of-concept of immunogenic cell death induction leading to effective adaptive immune response when combined with ICI. Recommended Phase 2 dose optimization and expansion cohorts in immunologically cold cancers are ongoing. Citation Format: Crescens Tiu, Wing Yau, Victoria Sanchez-Perez, Giovanni Codacci-Pisanelli, Ching Leung, Eden S. Andrews, Bristi Basu, Anna Zachariou, Toby Prout, Mona Parmar, Alison Turner, Xiaoran Lai, Zhulin Yin, Karen E. Swales, Syed Haider, Thomas Lund, Diego C. Dos Reis, Tatiany L. Silveira, Alan S. Dunlop, Ann-Marie Baker, Bora Gurel, Ana Ferreira, Claudia Bertan, Nina Tunariu, Edward W. Johnston, Alistair Ring, Tencho Tenev, Tomoko Smyth, Simone Jueliger, Udai Banerji, Johann S. de Bono, Alec Paschalis, Adam Sharp, Anna Minchom, Christina Yap, Pascal Meier, Juanita S. Lopez. Proof-of-concept and preliminary efficacy of triple IAP blockade to maximize immunogenic cell death and induce efficient adaptive immune response: First report on the ASTEROID phase 1 trial [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 CT035.

Venetoclax in Combination with Intermediate Doses of Cytarabine in Consolidation Phase for Acute Myeloid Leukemia Patients in First Complete Remission; Results of the Part 1 of the Phase 1/2 Multicentric Covenidac Study

For authors: Please: L Gastaud and P Peterlin: co-primary, H dombret et C Recher: co-last Background: The French ALFA-FILO AML intergroup launched the BIG-1 trial (EudraCT No.: 2014-000699-24) in 2015 to evaluate different intensive chemotherapy (ICT) strategies aiming at improving the survival of younger adults with acute myeloid leukemia (AML). All patients (pts) with previously untreated non-APL and non-CBF AML aged 18-60 years were eligible for this trial. The trial design included several randomization types. Results of the R1 and R2 randomizations, namely idarubicin vs daunorubicin for induction and IDAC vs HDAC for consolidation, will be reported at this meeting. In patients who achieved first complete remission (CR), randomizations R4 consisted of nested randomized Phase 2 or 1/2 studies evaluating the addition of new drugs to the IDAC/HDAC consolidation cycles. The protocol was designed to allow several sequential multicenter R4 evaluations of various new agents over the trial period. Venetoclax (VEN) has proved its efficacy when combined to azacitidine or low dose cytarabine in unfit AML pts (DiNardo et al. 2020; Wei et al. Blood 2020). Its role in fit patients treated with ICT is still under investigation. The COVENIDAC Phase 1/2 R4 sub-study is evaluating the safety and efficacy of VEN added to IDAC during the consolidation cycles of CR pts. We report herein the result of the Phase 1 part. Methods: The primary objective of this Phase 1 study was to determine the maximum tolerated dose (MTD) of VEN in combination with IDAC during the consolidation cycles, which will be the recommended dose for the Phase 2 (RP2D). Dose limiting toxicities (DLTs) were assessed during the first cycle of consolidation (C1) according to a 3+3 design. A maximum of 3 consolidation cycles was planned depending on the AML risk group. Hematological DLT was defined as no peripheral blood count recovery within 56 days from day 1 of the cycle. Non-hematological DLTs were defined as Grade ≥4 toxicities or Grade ≤3 toxicities which have not recovery by day 56 and deemed related to VEN per investigator opinion. VEN was started at dose level (DL) 1: 100 mg/d from day 1 to 8. In the absence of DLTs at DL1, 3 others DL were planned: 200 mg/d from day 1 to 8 (DL2); 400 mg/d from day 1 to 8 (DL3), and 400 mg/d from day 1 to 14 (DL4). IDAC was administrated at 1.5 gr/m² twice daily on day 1/3/5 for DL1, DL2 and DL3 pts, then on day 1/2/3 for DL4 pts after a protocol amendment. Main inclusion criteria were: pts in first CR following 1 or 2 courses of induction chemotherapy fit for further ICT; favorable and intermediate risk AML as defined by the protocol; ECOG PS ≤2; written informed consent. Measurable residual disease (MRD) was assessed by multiparametric flow cytometry (MFC) in all pts as well as NPM1-qPCR in NPM1-mutated pts. Results: Between 06/2021 and 04/2022, 15 pts from 9 centers were screened and enrolled. Pt characteristics were as follows: median age, 42 years (IQR, 30-49); 2 males/7 females; ECOG-PS, 0 in 10 pts and 1 in 5 pts; favorable/intermediate/adverse ELN-2017 risk, 9/2/4. Neutropenia and thrombocytopenia durations are shown in Table 1. Only 1 hematological DLT was observed at DL3 (platelet count of 96 giga/L at day 56 in a patient who was infected by Covid-19). Overall, there were very few non hematological AEs ( Table 2, no grade 4) and only 4 SAEs (1 related to IDAC/VEN during C1, 3 non-related). No non-hematological DLT was observed. No patient died during the DLT observation period, 1 experienced a septic shock (C2, DL2). One pt received only C1 (due to DLT), 7 received 2 cycles, and 7 received 3 cycles. Median time between initiation of subsequent consolidation cycles was 37.5 days (IQR, 35-41) for C1/C2 and 40 days (IQR, 35-43) for C2/C3. One pt had to stop VEN during C3. Six pts received an allogeneic HSCT (5 in CR1, 1 after salvage). With a median follow-up of 13.5 months, 3 pts relapsed and 2 died. MRD results will be presented. Conclusion: VEN/IDAC combination appears to be feasible and safe as consolidation therapy, with expected thrombocytopenia and neutropenia durations. These durations appeared even shorter at DL4, when IDAC was given on 3 consecutive days. VEN at 400 mg/d from day 1 to 14 combined with IDAC on day 1/2/3 was thus retained as RP2D for the randomized Phase 2 with RFS as primary endpoint. This phase 2 has already recruited 29 of the 200 pts planned.

TIM-3 Inhibitor Sabatolimab for Patients with Acute Myeloid Leukemia (AML) with Measurable Residual Disease (MRD) Detected after Allogeneic Stem Cell Transplantation (AlloSCT): Preliminary Findings from the Phase Ib/II Stimulus-AML2 Study

Introduction: AlloSCT is a potentially curative treatment for patients (pts) with AML. However, MRD persistence after transplantation has been identified as a risk factor for relapse. In this regard, the graft-versus-leukemia (GvL) effect is well recognized as one of the leading mechanisms of disease control after transplantation. Sabatolimab is a novel immunotherapy that targets the immuno-myeloid regulator TIM-3 on both immune cells and leukemic blasts, and may have the potential to enhance the GvL effect. STIMULUS-AML2 (NCT04623216) is a Phase Ib/II, open-label, multicenter study of sabatolimab alone or in combination with azacitidine as pre-emptive therapy in pts with AML who are in complete remission (CR) with positive MRD (MRD+) after alloSCT. Here we report preliminary data from the safety run-in of sabatolimab monotherapy at two dose levels (400 mg or 800 mg intravenous [IV] every four weeks [Q4W]). Methods: Eligible pts for the safety run-in were adults (≥18 years [y]) with de novo or secondary AML, who achieved CR post-alloSCT but were MRD+ by local assessment at any time ≥Day (D) 60 after alloSCT (protocol amended from MRD+ D100-365 post alloSCT; March 24, 2022) and ≥2 weeks after immunosuppressive medications had been tapered off. MRD was assessed locally at baseline by polymerase chain reaction (PCR; 12 pts: NPM1 and/or WT1, 8; IDH2, 2; other, 2), multiparameter flow cytometry (MFC; 6 pts), both PCR and MFC (1 pt), and CD34+ chimerism (2 pts). In this safety run-in, adult pts received sabatolimab monotherapy at 400 mg or 800 mg IV on D1 of every 28-day cycle. The primary endpoint was incidence of treatment-emergent dose-limiting toxicity (DLT), including acute graft-vs-host disease (GvHD) and chronic GvHD during the first 2 cycles. Results: A total of21 pts were enrolled in the safety run-in (10 at 400 mg; 11 at 800 mg). Median age was 59 years. At AML diagnosis, across cohorts, 8, 9 and 4 pts had favorable, intermediate, and adverse genetic risk (European LeukemiaNet 2017), respectively. At data cut-off (April 26, 2023), 3 pts were still ongoing in the 400 mg cohort and 7 had discontinued due to disease relapse. At 800 mg, 4 pts were ongoing and 7 had discontinued (5 due to relapse, 1 due to adverse event [AE], 1 due to new therapy) ( Table 1). Across cohorts, there was 1 DLT of grade (G) 3 myocarditis after the first infusion of sabatolimab 800 mg, which recovered/resolved on the same day and sabatolimab was then withdrawn. An overview of safety is shown in Table 2. Any G and G≥3 AEs occurred in 16 (76.2%) and 8 (38.1%) pts, respectively. There were no cases of GvHD or immune-related AEs, 2 cases of G≥3 neutropenia and 1 case of G≥3 thrombocytopenia. G3 neutropenia and G3 thrombocytopenia in the same pt at 400 mg were considered treatment related and the patient later relapsed. At 400 mg, 2 pts experienced serious AEs (SAEs) after the DLT observation period (>3 cycles) and 2 pts at 800 mg had SAEs during the DLT period (G3 myocarditis [1 pt] and disease relapse with central nervous system involvement [1 pt]). There were 5 deaths, all at 400 mg and due to study indication (AML). As a preliminary indicator of efficacy, 7 pts were still on treatment and in CR at data cut-off. At 400 mg, 2 pts and 1 pt had received 14 and 15 cycles of treatment (>1 y), respectively. At 800 mg, 1 pt had received 5, 1 pt 6, and 2 pts 7 cycles. At 400 mg, 7 pts relapsed: 2 pts after cycle 1, 2 pts after cycle 2, 1 pt each after cycles 3, 4 and 7. At 800 mg, 5 pts relapsed: 1 pt after cycle 1, 2 pts after cycle 2, 1 pt after cycle 3 and 1 pt after cycle 5. Conclusions: In adult pts with AML who are in hematological CR with MRD+ after alloSCT, sabatolimab 400 mg and 800 mg monotherapies were well tolerated. Cytopenias occurred at low rates, were generally G1-2 and mostly related to imminent relapse. Importantly, there were no cases of GvHD reported or any immune-related AEs commonly seen with checkpoint inhibitors. Preliminary efficacy was promising with 30% of the pts at 400 mg still in CR after more than 1 y on treatment (available longer-term follow-up >1 y), and data may suggest a delayed onset of relapse. A dose expansion cohort at 800 mg opened for enrollment June 30, 2023. Adults will be randomized to sabatolimab as monotherapy or in combination with azacitidine, and preliminary efficacy on the prevention of hematological relapse will be evaluated. Adolescents (12-17 y) will also be enrolled to evaluate the safety of sabatolimab monotherapy. This study is sponsored by Novartis.

Phase 1 trial of avelumab with hypofractionated thoracic radiation therapy (HT-RT) in patients with metastatic soft-tissue sarcomas (mSTS).

11552 Background: Combining HT-RT with anti PD-L1 therapy may enhance local and distant tumour control in mSTS. This was a Phase 1 trial to evaluate the safety, tolerability, and efficacy of avelumab in patients with mSTS. Methods: This was a single centre phase 1 trial of avelumab with HT- RT in patients with mSTS (NCT03602833). Patients > 18 years with at least 2 pulmonary metastases, ECOG performance status 0-1 were eligible between Oct 2018-Apr 22. Patients received HT-RT (36 Gy in 12 fractions), with concurrent intravenous avelumab (10 mg/kg q14d) until disease progression. The primary end point was safety of avelumab with HT-RT. Secondary endpoints included local control rate at 3 months. Dose limiting Toxicity (DLT) assessed from start of HR-CT and avelumab up to Cycle 7 avelumab and defined as: ≥ G2 pneumonitis, ≥ G2 myelitis, ≥ G3 non-haem toxicity, ≥ any other G4 and/or HT-RT interruption > 5 days. Response was evaluated using the Response Evaluation Criteria in Solid Tumors (RECIST). Results: 12 patients were treated in this trial. Histological subtypes: leiomyosarcoma (n = 2), undifferentiated pleomorphic sarcoma (n = 2), and spindle cell sarcoma (n = 2). The median age was 57.5 (37-68) years, 7 were female (58%). All patients had lung metastases. 1 previously received SBRT to the lung, and 5 (42%) patients had received prior systemic treatment. 12 patients received at least one cycle of avelumab, median 9 (range: 1-37), and treatment was discontinued in 11 (92%) patients; 10 (83%) stopping for progressive disease, 1 (8%) patient for G4 immune-mediated hepatitis after DLT period and 1 patient completed and continues on compassionate-use avelumab. Eleven (92%) completed radiotherapy (36 Gy, 12 fractions). No DLTs or treatment-related deaths were observed. HT-RT toxicity: 3 G2 acute (1 oesophagitis, 2 skin) noted up to 11 weeks. 13 G1 late toxicities (5 pneumonitis, 5 skin, 1 cardiac, 1 myelitis, 1 oesophagitis) reported. Avelumab toxicities: 2 G3 (1 ALT rise, 1 viral infection) and 3 G4 (1 AST rise, 1 hepatitis, 1 sepsis) reported after DLT observation period. The median follow-up was 21.8 (range 3.2-31.9) months with a 3-month local control rate of 50% (95% CI, 21%-74%). RECIST responses at 3 months were 0 CR, 1 (8%) PR, 5 (42%) SD and 5 (42%) PD. Conclusions: Avelumab in combination with thoracic radiotherapy was safe with encouraging anti-tumour activity in patients with metastatic soft-tissue sarcomas. Additional molecular biomarker analyses are in progress. Clinical trial information: NCT03602833 .

Safety, tolerability, and pharmacokinetics of HLX26 (an anti-LAG3 antibody) in patients with advanced or metastatic solid tumors or lymphomas.

e14671 Background: HLX26 is a novel humanized anti-LAG3 monoclonal antibody. This study aimed to evaluate the safety, tolerability, and pharmacokinetics of HLX26 in patients with advanced or metastatic solid tumors or lymphomas. Methods: This was a first-in-class, multicenter, open-label, dose-escalation phase 1 study. Patients with histologically or cytologically confirmed advanced solid tumors or lymphomas who had failed or were not suitable for standard therapies were enrolled and received HLX26 at five dose levels (60, 150, 300, 500, or 800 mg, Q3W) intravenously. This study followed accelerated titration combined with a “3+3” design. HLX26 was given until disease progression with no clinical benefit, 2 years of treatment, experiencing intolerable toxicity, withdrawal of consent, or death, whichever occurred first. The primary endpoints were dose-limiting toxicities (DLTs) and maximum tolerated dose (MTD) within DLT observation period, which was 3 weeks after the first dose of HLX26. Secondary endpoints included safety, pharmacokinetic and pharmacodynamic characteristics, preliminary efficacy, immunogenicity, and potential biomarker explorations of HLX26. Results: As of December 22, 2022, 12 patients with stage IV breast (n = 10, 83.3%) or rectum (n = 2, 16.7%) solid tumors were enrolled and received HLX26 at 60 mg (n = 1), 150 mg (n = 1), 300 mg (n = 3), 500 mg (n = 3), or 800 mg (n = 4). The mean age was 57.5 (range 31–73) years. No DLT was reported and the MTD was not determined as of yet. Eleven (91.7%) patients experienced treatment-emergent adverse events (TEAEs), most commonly hypercholesterolemia (41.7%), hypertriglyceridemia (25.0%), and hyperuricemia (25.0%). Most TEAEs were grade 1 (n = 8, 66.7%) and 2 (n = 2, 16.7%). Conclusions: In summary, no new safety signals were observed from 60 mg to 800 mg of HLX26. HLX26 was safe and well tolerated in patients with advanced or metastatic solid tumors. Clinical trial information: NCT05078593 .

A phase 1b, open-label, two-part safety, tolerability, and efficacy study of a soluble beta-glucan (odetiglucan) in combination with a CD40 agonistic monoclonal antibody (CDX-1140) in patients with metastatic pancreatic adenocarcinoma whose disease did not progress during first-line (1L) chemotherapy.

TPS4201 Background: Metastatic pancreatic ductal adenocarcinoma (PDAC) is an aggressive and lethal disease with a 5-year overall survival (OS) rate of 3%. Standard of care treatment is continuous cytotoxic chemotherapy which produces modest improvements in OS but is also associated with significant toxicity raising the need for novel treatment paradigms. Although immunotherapy has yet to produce clinical benefit for most patients with PDAC, preclinical modeling demonstrates its potential and show that combinations of myeloid agonists can trigger robust synergistic anti-tumor activity against PDAC tumors that are otherwise resistant to immunotherapy including immune checkpoint blockade (anti-CTLA4, anti-PD1). In this study, odetiglucan (OD), a novel beta glucan pathogen associated molecular pattern (PAMP), will be combined for the first time with CDX-1140, a fully human Ig2K agonistic monoclonal CD40 antibody in the maintenance setting after an induction phase of cytotoxic chemotherapy. OD and a CD40 agonist directly promote the activation and maturation of antigen presenting cells and shift the suppressive TME to enhance T-cell responses through non-redundant myeloid signaling pathways. We hypothesize that the combination of OD and CD40 agonist therapy has the potential to trigger anti-tumor immunity in PDAC and thus, extend and deepen responses to 1L cytotoxic chemotherapy. Methods: A two-part Phase 1b study of metastatic PDAC pts who have evidence of response or stable disease following 16-24 wks of chemotherapy is being conducted. Part A uses a 3+3 design; pts will receive OD 4 mg/kg QW + CDX-1140 1.5 mg/kg Q3W. Following a dose-limiting toxicity observation period, the dose will be held at 1.5 mg/kg or decreased to 0.72 mg/kg Q3W. Once preliminary safety is established, the cohort will be expanded to 15 pts. Part B pts will receive OD 4mg/kg + CDX-1140 at the dose identified in Part A Q3W. The study will enroll 30 pts. Main eligibility criteria: Metastatic PDAC having durable stable disease or response to 1L chemotherapy; serum ABA ≥20 µg/mL, and no prior anti-CD40 mAb or immunomodulatory treatment exposure. Primary endpoints are MTD, RP2D, and safety. Secondary endpoints include DOR, PFS, ORR, and OS and exploratory endpoints include evaluating immune pharmacodynamic responses in peripheral blood and tumor. Safety parameters will be listed and summarized using descriptive statistics. ORR will be tabulated by overall frequency; DOR, TTF, PFS and OS will be summarized and presented using Kaplan-Meier and waterfall plots. 5 US sites will participate. Clinical trial information: NCT04834778 .

Trial in Progress: A Phase II Window of Opportunity Study of the BCMAxCD3 Bispecific Antibody REGN5458 in Previously Untreated Patients with Symptomatic Multiple Myeloma

Background Treatment of multiple myeloma (MM) has advanced significantly in the last 20 years, resulting in improved survival. For patients with newly diagnosed MM (NDMM) who are fit with no comorbidities, currently recommended treatment includes induction with triplets such as bortezomib, lenalidomide, and dexamethasone (VRd), followed by high-dose chemotherapy (HDT) and autologous stem cell transplantation (ASCT), and maintenance therapy using predominantly immunomodulatory agents. Patients who are elderly or ineligible for HDT/ASCT receive multiple drug combination therapies such as VRd or daratumumab with Rd. Despite the availability of these combinations, induction therapy does not induce complete remission with minimal residual disease negativity in all patients, and triplet- or quadruplet-based regimens are expensive and associated with enhanced toxicities including to stem cells. Moreover, MM remains incurable and new therapies with alternative mechanisms may improve or maintain the safety profile while increasing or deepening responses for longer periods. B-cell maturation antigen (BCMA) is a cell surface protein expressed on malignant plasma cells (Lee, et al. Br J Haematol. 2016;176:911-22). Notably, BCMA is detected only at low levels on normal plasma cells, activated B cells, and plasmacytoid dendritic cells, making it an attractive therapeutic target for MM. REGN5458 is a BCMA×CD3 bispecific antibody capable of binding to BCMA on MM cells and CD3 on T cells, inducing T-cell mediated cytotoxicity of MM cells. REGN5458 monotherapy has demonstrated early, deep, and durable responses with a manageable safety and tolerability profile in patients with relapsed/refractory (R/R) MM (NCT03761108; Zonder, et al. EHA 2022. Abstract S189) with a response rate of 75% among patients treated at the 200-800 mg dose levels. Cytokine release syndrome was reported in 38% of patients and was mostly Grade 1, with no Grade ≥3 events. Given the single agent efficacy and tolerability of REGN5458 in heavily pre-treated patients with R/R MM, its use in patients with NDMM (who are thought to potentially have improved T-cell fitness versus R/R patients) is hypothesized to have enhanced therapeutic benefit. Study Design and Methods This open-label, Phase II study aims to assess the safety, tolerability, pharmacokinetics (PK), and preliminary efficacy of REGN5458 monotherapy in patients with NDMM who are eligible or ineligible for HDT/ASCT. Transplant-eligible patients will receive REGN5458 induction, HDT/ASCT, followed by REGN5458 consolidation, and standard of care maintenance therapy. Transplant-ineligible patients will receive REGN5458 until disease progression or other discontinuation criteria are met (Figure). The primary objectives during part 1 are to assess safety and tolerability and to determine a recommended regimen for expansion. The objective for dose expansion is to assess preliminary antitumor activity. Secondary objectives are to evaluate the PK properties and immunogenicity of REGN5458 as well as soluble BCMA concentrations in serum at baseline and over time. The primary endpoints for part 1 are: the incidence of dose-limiting toxicities (DLTs) from the first dose of study drug to the end of the DLT observation period; the incidence and severity of treatment-emergent adverse events and adverse events of special interest with REGN5458 through study completion; for expansion: the proportion of patients with a very good partial response or better as determined by the investigator using International Myeloma Working Group response criteria; and the proportion of patients achieving minimal residual disease-negative status (at 10-5). Patients will have a window of opportunity to benefit from treatment; patients who do not meet the specified efficacy thresholds will transition to standard of care therapies. Approximately 92 patients are planned for this study. Eligibility criteria include age ≥18 years; ECOG PS 0-2; histologically or cytologically confirmed symptomatic MM; measurable disease; no prior therapy for MM, except radiation on an emergency/palliative basis or 1 month of single-agent corticosteroid if the patient still has measurable disease; and adequate bone marrow reserves, hepatic, renal, and cardiac function. The study will take place in approximately 20 sites located in North America and Europe. There are no formal hypothesis tests for this study. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

CTNI-53. PNOC014: PHASE IB STUDY RESULTS OF DAY101(TOVORAFENIB) FOR CHILDREN WITH LOW-GRADE GLIOMAS (LGGS) AND OTHER RAS/RAF/MEK/ERK PATHWAY-ACTIVATED TUMORS

Abstract BACKGROUND Pharmacokinetic modeling for previously reported phase 1A data of pan-RAF inhibitor DAY101 in RAS/RAF/MEK/ERK pathway-altered tumors suggested a correlation between higher doses and improved efficacy without clear safety data. The protocol was amended to explore differential dosing across different body surface areas (BSA). METHODS Eligible patients were < 25 years old with radiographically recurrent/progressive RAS/RAF/MEK/ERK pathway-altered tumors. We applied a novel modification of a TITE-BOIN design to determine recommended phase 2 dosing of oral, weekly DAY101 in evaluable patients within two BSA subgroups: ≤ 1.5 m2 or > 1.5 m2. Target toxicity probability was closest to 20%. We tested 420 and 530 mg/m2. Dose limiting toxicities (DLTs) were determined within Cycle 1. Evaluable patients had either ‘complete’ or ‘partial’ information. Complete information meant patient had a DLT or received 3 of 4 planned doses with no DLT. Partial information meant patient received only 1 or 2 doses or did not complete the DLT observation period. Three patients with complete information at a given dose level were required before dose escalation. The primary endpoint driving dose escalation was time from start of Cycle 1 to first DLT or, if no DLT, time from start of Cycle 1 to minimum of date of last contact or end of Cycle 1. RESULTS We treated 35 eligible patients: 21 KIAA1549:BRAF-, 9 BRAFV600E-, 4 novel RAF- and one FGFR1-altered tumors. Histologically, cohort included 30 LGGs, 4 high grade gliomas and 1 soft tissue sarcoma. There were 6 DLTs: 3 in each BSA subgroup, all at 530 mg/m2/dose, all grade 3, and 5 known side effects ( 2 fatigue, 3 rash, 1 menorrhagia). CONCLUSIONS Oral weekly DAY101 is well tolerated. The TITE model recommends 530 mg/m2/dose PO weekly for patients with BSA < 1.5m2 and 420 mg/m2/dose PO weekly for patients with BSA >1.5m2.

Phase I trial of single-agent recombinant human anti-vascular endothelial growth factor (GB222) followed a combination therapy of GB222 and temozolomide in patients with recurrent WHO grade III and IV glioma

BackgroundTreatment options for malignant and aggressive glioma are limited. Vascular endothelial growth factor (VEGF) antibodies are angiogenesis inhibitors that prevent the growth of neoplasms by inhibiting the expansion of the vascular tissue that supports them. We designed this phase I trial to assess the safety and establish the maximum tolerable dose (MTD) of GB222, a recombinant human anti-VEGF monoclonal, for patients with recurrent malignant glioma.MethodsEligible patients were those who were diagnosed with WHO grade III and IV glioma and progressed after initial treatment including surgery, radiotherapy, and temozolomide. GB222 was initiated at 3 mg/kg (Cohort 1) intravenously once every four weeks (Q4W), then escalated in a 3 + 3 design at 5 mg/kg (Cohort 2, Q4W), 5 mg/kg (Cohort 3, Q2W), 7.5 mg/kg (Cohort 4, Q2W), and 10 mg/kg (Cohort 5, Q2W). The initial 28 days of each dose level cohort was the observation period for dose-limiting toxicity (DLT). After that, patients continued the treatment with the same dose of GB222 in combination of temozolomide if patients were considered to have benefited from the treatment. Our study also evaluated anti-tumor efficacy including objective response rate (ORR), progress free survival (PFS), and overall survival (OS), as well as pharmacokinetic parameters of GB222.FindingsSixteen patients were enrolled: 4 in Cohort 1, 3 each in Cohort 2, 3, 4, and 5. In the 28 days with GB222 alone, no DLT events were observed in all dose cohorts, and MTD was not reached. Among 16 patients, 14 (87.5%) received the combined treatment of GB222 and temozolomide after the DLT observation period. Two patients stopped the treatment after the DLT observation period due to disease progression. All patients (100%) reported experiencing at least one adverse event (AE) among patients who either received GB222 alone or the combination therapy of both GB222 and temozolomide. Four patients experienced grade 3/4 AE (one in Cohort 1, one in Cohort 2, and two in Cohort 3), including status epilepticus, herpes zoster, bone marrow failure, and hematological laboratory abnormalities. None of them was determined to be GB222 related. No death and treatment termination occurred due to AEs. Among these 16 patients, 81.3% (13/16) had treatment-related adverse events (TRAE). The common TRAE included decreased neutrophil count, decreased leukocyte count, increased alanine aminotransferase, hypertension, and rash. Pharmacokinetics (PK) studies showed drug exposure of GB222 had a linear relationship with the dose administrated. The overall objective response rate among 16 patients was 31.3% (95% CI: 11.02%, 58.66%) with 0% in Cohort 1, 66.7% in Cohort 2 (1 CR and 1 PR), 33.3% in Cohort 3 (1PR), 0% in Cohort 4, and 66.7% in Cohort 4 (2 PR). The median PFS was 4.44 months [95% confidence interval (CL) 2.76–6.60 months]. The median OS was 8.38 months (95% Cl: 4.24-not reached).InterpretationGB222 alone or combined with temozolomide had manageable safety profiles and encouraging anti-tumour activity in treating patients with recurrent HGG.

Abstract CT240: A first-in-human study of the dual A2A/A2B adenosine receptor antagonist M1069 in patients with advanced solid tumors

Abstract A2A and A2B adenosine receptors have been shown to mediate immunosuppressive and tumor-promoting signals in the tumor microenvironment and their inhibition may be a promising treatment strategy for patients with advanced solid tumors. Dual A2A/A2B inhibition has shown an acceptable safety profile as monotherapy and early signs of clinical activity in combination with chemotherapy in patients with advanced solid tumors. M1069 is a novel, orally administered, highly selective dual antagonist of the A2A and A2B adenosine receptors that has recently demonstrated significant anti-tumor activity in vivo as monotherapy and in combination with chemotherapeutic agents in adenosine-rich tumor models. The aim of this Phase Ia First in Human noncontrolled, open-label, multicentre, dose escalation clinical study (NCT05198349) is to investigate the safety, tolerability, pharmacokinetics, pharmacodynamics and preliminary activity of M1069 in patients with metastatic or locally advanced unresectable solid tumors. Study Design: Patients aged ≥18 years, with an Eastern Cooperative Oncology Group performance status ≤1, adequate baseline hematological, renal and hepatic function, and with locally advanced or metastatic disease refractory to, or who have progressed with, standard therapy are eligible. Patients who have had prior treatment with another agent targeting the adenosine signalling pathway or prior anticancer treatment within 4 weeks or 5 half-lives are excluded. The study includes a 28-day screening period, a study intervention period of 21-day cycles, a 21-day dose-limiting toxicity observation period, an end of study intervention visit and a safety follow-up period of 30±7 days. Patients (approximately 21-30) will receive M1069 monotherapy twice daily in 21-day cycles until disease progression, unacceptable toxicity, withdrawal of consent or any criterion for withdrawal from study intervention. The starting dose is M1069 150 mg twice daily, with dose escalation decisions (300, 450, 600 and 700 mg twice daily) made by the safety monitoring committee and supported by results of a Bayesian Logistic Regression Model (BLRM). The primary objectives of the study are to determine the dose toxicity relationship and maximum tolerated dose (MTD), if reached, of M1069 and to determine the recommended dose for expansion of M1069 for further exploratory clinical development. These will be measured by the occurrence of dose-limiting toxicities, adverse events and treatment-related adverse events, and, through analysis of the safety, tolerability, pharmacokinetics, pharmacodynamics and post-treatment changes in the tumor microenvironment in available paired tumor biopsies, respectively. The target dose-limiting toxicity probability for the MTD is 30% which will be estimated by the BLRM. Pharmacokinetic parameters will be calculated using noncompartmental analysis. The study is open and patients are being treated at the first dose level. Citation Format: Lillian L. Siu, Martin E. Gutierrez, Guelseren Guezel, Katia Ruth, Ping Hu, Thomas Kitzing, Christina Habermehl, Meredith McKean. A first-in-human study of the dual A2A/A2B adenosine receptor antagonist M1069 in patients with advanced solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT240.

NRG-DT001 phase Ib trial of neoadjuvant navtemadlin (previously AMG232 and KRT232) concurrent with preoperative radiotherapy in wild-type p53 soft tissue sarcoma of the extremity and body wall.

11521 Background: NRG-DT001 is a phase Ib trial evaluating neoadjuvant navtemadlin with preoperative radiation therapy (RT) in patients (pts) with wild-type (WT) p53 soft tissue sarcoma (STS). The primary objective is to evaluate the safety and tolerability of the MDM2 inhibitor navtemadlin in combination with standard-dose RT in STS in two cohorts (A, extremity or body wall; B, abdomen/pelvis/retroperitoneum) to determine the maximum tolerated dose/recommended phase II dose (MTD/RP2D) of navtemadlin in combination with RT. This report contains the results for cohort A. Methods: Eligible pts had grade 2-3 STS ≥ 5 cm, age ≥ 18, and Zubrod performance status 0-1. Dose levels were 120 mg 2x/week (DL-1), 120 mg 3x/week (DL1), 4x/week (DL2), and 5x/week (DL3) 1 week prior to and during RT (50Gy/5 weeks). Surgery was 5-8 weeks after RT. A 3+3 design was used to make dose escalation/de-escalation decisions at each dose level. Five additional pts were enrolled to the MTD to ensure safety (expansion cohort) with a dose limiting toxicity (DLT) rate of ≤ 1/5 considered safe. The DLT observation period was from the start of navtemadlin until 4 weeks after completion of drug+RT. Tumor Tp53 mutation status was determined by NGS sequencing. All eligible and treated p53 WT pts who experienced DLT or completed the observation period were considered DLT-evaluable. DLT included all grade 4-5 AE definitely, probably, or possibly related to navtemadlin. Any grade 3 AE definitely, probably, or possibly related to navtemadlin was also considered DLT if any of the 2 following situations occurred: a delay of treatment > 2 weeks or ≥ 2 dose reductions due to the grade 3 AE. The decision to escalate or de-escalate was made by consensus of the study team in accordance with the protocol. Results: Between 11/3/2017 and 9/10/2021, 4 (3 WT), 7 (4 WT) and 7 (4 WT) pts were enrolled at DL1, DL2, and DL3 respectively. An additional 9 (5 WT) pts were enrolled on DL3 expansion cohort. Preoperative RT was completed for all except 1 pt (pt refusal/DL3). On DL1 and DL2, 100% of pts completed navtemadlin. On DL3 (including expansion cohort), 78% (7/9) completed navtemadlin (1 AE, 1 pt refusal). On DL1, DL2, and DL3, 3/3, 3/4 (1 disease progression), and 5/6 (1 consent withdrawal; 3 pending) completed surgery. There were no DLTs in any dose level (DL1 0/3, DL2 0/4, DL3 0/9), establishing DL3 as the MTD/RP2D. Tumor necrosis rates will be reported at the time of presentation. Conclusions: Neoadjuvant navtemadlin concurrent with standard dose preoperative RT is well tolerated in patients with WT p53 STS at extremity or body wall, and the 120 mg PO daily of navtemadlin, 5 days per week dose should be used to design future trials of RT with extremity STS. Incorporating NGS sequencing results as an integral biomarker in a clinical trial of neoadjuvant radiotherapy and a radiosensitizer is feasible. Clinical trial information: NRG-DT001 NCT03217266.

A Phase 1 Study of XmAb18968, a CD3-CD38 Bispecific Antibody for the Treatment of Patients with Relapsed/Refractory Acute Leukemia and T Cell Lymphoblastic Lymphoma

Abstract Background: Outcomes of adults with relapsed/refractory T-cell acute lymphoblastic leukemia or lymphoma (T-ALL or T-LBL respectively) and acute myeloid leukemia (AML) have remained poor despite the availability of newer agents. CD38 is a 45 kDa transmembrane glycoprotein expressed by lymphoid and myeloid cells with several important functions including a role in immune escape from tumor cells [Chillemi A et al. Front Immunol 2017, Furano A et al. J Immunol 1990]. Several studies have demonstrated that CD38 is expressed in tumor cells of patients with T-ALL and AML and potentially targetable using CD38 blocking agents [Naik J et al. Haematologica 2019, Bride KL et al. Blood 2018, Tembhare et al. J Immunother Cancer 2020, Farber M et al. ASH 2018]. XmAb18968 is structurally distinct CD3-CD38 bi-specific T-cell engager with a full fragment crystallizable (Fc) domain modified to minimize Fcγ receptor binding and non-selective activation of T cells and other immune effector cells. XmAb18968 has optimized relative affinities for both CD3 and CD38 which results in reduced cytokine release without compromising target cell killing. We hypothesize targeting CD38 in relapsed/refractory- T-cell ALL/LBL and AML is safe and feasible using XmAb18968, a novel CD3-CD38 bispecific antibody. Study design and methods: This is an investigator-sponsored multi-institutional phase I study evaluating the safety and tolerability of XmAb18968. Patients aged 18 years or above with T-ALL, T-LBL or AML (including undifferentiated leukemia and bi phenotypic leukemia), in relapsed/refractory status (at least one line of prior therapy) including measurable residual disease relapse, CD38 expression ≥ 20%, and adequate organ function will be eligible. Major exclusion criteria are hematopoietic cell transplantation (HCT) within 6 months of enrollment, active acute GVHD, veno-occlusive disease, and acute promyelocytic leukemia. The study is planned to be conducted at 6 sites in United States. The primary endpoint is to determine the recommended phase 2 dose (RP2D) and toxicity profile of XmAb18968. The secondary endpoints include determination of response rates, duration of response, survival and pharmacokinetics. Exploratory endpoints include correlation of responses with genomic profile, assessment of serum cytokine response, identifying the changes in phenotypic expression of activated T-cells and leukemic cells, correlation of the phenotypic expression with changes in the transcriptome at the single-cell level, proteomics evaluation of cytokine secretion at the single-cell level and correlation of response with N-glycan profiling, quantitative site-occupancy and direct glycopeptide analysis. The study will follow 3+3 design for dose escalation and de-escalation in case of dose limiting toxicity (DLT). Dose escalation will proceed in two separate groups: Group A for subjects with T-ALL and T-LBL and Group B for subjects with AML. Patients will be entered sequentially to each dose level, starting with the first dose level. The DLT observation period for dose-escalation will be 28-days. RP2D will be defined as the highest dose level at which none of the first 3 treated subjects, or no more than 1 of the first 6 treated subjects experience a DLT. A minimum of 24 and a maximum of 60 patients will be needed for the dose escalation phase. Disclosures Guru Murthy: Curio Sciences: Honoraria; Techspert: Consultancy; Qessential: Honoraria; CancerExpertNow: Honoraria; DAVA Oncology: Honoraria; TG Therapeutics: Other: Advisory board meeting; Cardinal health: Honoraria; Guidepoint: Consultancy. Johnson: Miltenyi Biotec: Research Funding. Abedin: AltruBio: Research Funding; Amgen: Honoraria; Agios: Honoraria; Helsinn: Research Funding; Pfizer: Research Funding; Astellas Pharma Inc.: Research Funding; Actinium: Research Funding. Stock: Pfizer: Consultancy, Honoraria, Research Funding; amgen: Honoraria; agios: Honoraria; jazz: Honoraria; kura: Honoraria; kite: Honoraria; morphosys: Honoraria; servier: Honoraria; syndax: Consultancy, Honoraria; Pluristeem: Consultancy, Honoraria. Shah: Precision Biosciences: Consultancy; Kite, a Gilead Company: Consultancy, Honoraria, Other: Expenses, Research Funding; Pharmacyclics/Janssen: Honoraria, Other: Expenses; Acrotech/Spectrum: Honoraria; BeiGene: Consultancy, Honoraria; Amgen: Consultancy; Pfizer: Consultancy, Other: Expenses; Novartis: Consultancy, Other: Expenses; Bristol-Myers Squibb/Celgene: Consultancy, Other: Expenses; Adaptive Biotechnologies: Consultancy; Servier Genetics: Other; Jazz Pharmaceuticals: Research Funding; Incyte: Research Funding. Leonard: Amgen: Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees. Pratz: Agios: Consultancy; BMS: Consultancy, Honoraria; Novartis: Consultancy; Astellas: Consultancy, Honoraria, Research Funding; Cellgene: Consultancy, Honoraria; Millenium: Research Funding; University of Pennsylvania: Current Employment; Abbvie: Consultancy, Honoraria, Research Funding. Luger: Syros: Honoraria; Agios: Honoraria; Daiichi Sankyo: Honoraria; Jazz Pharmaceuticals: Honoraria; Brystol Myers Squibb: Honoraria; Acceleron: Honoraria; Astellas: Honoraria; Pfizer: Honoraria; Onconova: Research Funding; Celgene: Research Funding; Biosight: Research Funding; Hoffman LaRoche: Research Funding; Kura: Research Funding. Badar: Pfizer Hematology-Oncology: Membership on an entity's Board of Directors or advisory committees. Atallah: Novartis: Consultancy, Honoraria, Research Funding; Amgen: Consultancy; Abbvie: Consultancy, Speakers Bureau; Takeda: Consultancy, Research Funding; BMS: Honoraria, Speakers Bureau; Pfizer: Consultancy, Research Funding.

Trials in progress: A phase 1, open-label, dose-escalation, pharmacokinetic, safety and tolerability study of the selective TAM kinase inhibitor PF-07265807 in patients with advanced or metastatic solid tumors.

TPS2671 Background: MERTK is a receptor tyrosine kinase from the tumor-associated macrophage kinase (TAMK) family that regulates key aspects of immune homeostasis and responses to infection. MERTK inhibition may lower the threshold for immune activation thereby promoting anti-tumor activity. Agents with some degree of MERTK inhibitory activity have been investigated in the clinic, but are limited by poor potency in patients (pts) and significant off-targets effects. PF-07265807 (ARRY-067) is a selective small-molecule inhibitor of the TAMKs MERTK and AXL. In preclinical models, PF-07265807 monotherapy shows antitumor activity that results in long-term cures and resistance to tumor re-challenge when combined with anti-programmed cell death protein 1/programmed death-ligand 1 (anti-PD-1/PD-L1) antibodies. This first-in-human study will evaluate the safety, tolerability, pharmacokinetics (PK) and preliminary anti-tumor activity of PF-07265807 in pts with selected advanced or metastatic solid tumors. This study will also explore the potential utility of PF-07265807 in combination with anti-PD-1/PD-L1 antibodies. Methods: This is a phase 1, open-label, multi-center, dose-escalation study (NCT04458259) to evaluate the safety, PK and tolerability of PF-07265807. Eligible participants will be adult pts with selected advanced or metastatic solid tumors who are intolerant or resistant to standard therapy. Other key eligibility criteria: measurable disease by RECIST 1.1 or non-measurable disease; Eastern Cooperative Oncology Group performance status 0–2; adequate bone marrow, renal and liver function; and resolved acute effects of any prior therapy. Successive cohorts of pts will receive escalating doses of PF-07265807 starting from 25 mg QD. Each cycle will be 21 days in duration (14 days on/7 days off). Study drug treatment will continue until disease progression or unacceptable toxicity, whichever occurs first. For dose escalation, a Bayesian logistic regression model will be used to model the relationship of dose-limiting toxicities (DLTs) to PF-07265807 dose. This model, along with escalation with overdose control, will guide the dose escalation of PF-07265807 after the completion of the DLT observation period (first two cycles of treatment, i.e. 42 days) of each cohort, until determination of the maximum tolerated dose/recommended phase 2 dose (MTD/RP2D). After the MTD/RP2D is identified, the safety and efficacy of combined PF-07265807 and anti-PD1/PD-L1 treatment will be explored. Primary endpoints: incidence of DLTs, treatment-emergent adverse events and laboratory abnormalities. Secondary endpoints: PK parameters of PF-07265807, objective response rate and duration of response. The study began enrolling pts in September 2020 and is still recruiting. Clinical trial information: NCT04458259.

Abstract OT-27-01: PALVEN: A phase 1b study of palbociclib, letrozole and venetoclax in estrogen receptor, BCL2-positive metastatic breast cancer

Abstract Background: CDK4/6 inhibitors are integral to the treatment of Estrogen Receptor (ER) positive metastatic breast cancer (MBC). Although they are potent inhibitors of proliferation, tumor cell death (by apoptosis) may be curtailed. Venetoclax, an inhibitor of the pro-survival protein BCL2, has shown promise in an early phase clinical trial in ER+ MBC1. Moreover, preclinical studies suggest that venetoclax could improve tumor response to endocrine therapy and a CDK4/6 inhibitor by triggering apoptosis, including in growth arrested/senescent cells2. PALVEN is a phase 1b study (NCT NCT03900884), aiming to combine venetoclax with letrozole and the CDK4/6 inhibitor palbociclib. Trial Design: Eligible patients will be treated with letrozole (2.5 mg), palbociclib (75-125 mg) and venetoclax (100-800 mg) using a 3+3 dose escalation study design, with a maximum of 6 patients per dose cohort. Both palbociclib and venetoclax will be administered on day 1-21 of a 28 day cycle. Dose limiting toxicity (DLT) will be evaluated in the first 4 weeks of treatment. Tumor assessment will be performed every 8 weeks for 24 weeks and then every 12 weeks until progression. The primary endpoint is to describe DLTs reported within the first 4 weeks of treatment and determine the maximum tolerated dose (MTD), in order to define a recommended phase 2 dose (RP2D). Secondary endpoints include type and worst grade adverse events per patient (CTCAE v5.0), tumor response (RECIST v1.1), clinical benefit rate (CBR), progression free and overall survival (PFS, OS) as well as patient reported outcomes. Exploratory endpoints include metabolic response (using FDG-PET), changes in circulating tumor DNA (ctDNA), peripheral blood leukocyte subsets, and tumor phenotype in paired and progression biopsies. Eligibility Women with ER+ (≥10% positively stained carcinoma cells) and BCL2+ (≥50% cells with at least moderate cytoplasmic staining; intensity 2-3 on a 0-3 scale), unresectable locally advanced or MBC are eligible. Patients must have measurable or evaluable disease as per RECIST v1.1 and ECOG performance score of 0-1. Participants must not have had >2 prior lines of treatment in the metastatic setting and no previous treatment with CDK4/6 inhibitor or venetoclax in the adjuvant or metastatic setting. Statistical methods This is a proof-of-concept, dose escalation study and any statistical analysis of responses will be exploratory. Analysis will be focused primarily on adverse events, particularly DLTs reported in the DLT observation period. All secondary endpoints will be analysed separately combining all dosing cohorts. The response rate and CBR will be estimated with 95% confidence intervals calculated using exact methods based on the binomial distribution. Time-to-event endpoints (PFS and OS) will be described using Kaplan-Meier methods to calculate the median survival. Response rate, CBR and time-to-event endpoints (PFS and OS) will also be described for patients treated in the 1st versus 2nd and 3rd line setting. Accrual Target accrual is 6-36, depending on the number of dose cohorts required to reach DLT. Recruitment is active at 2 sites in Australia. References 1 Lok, S.W., et al. (2019). Cancer Discov 9, 354-369. 2 Whittle, J.R., et al. (2020). Clin Cancer Res Advance online. Citation Format: Christine Muttiah, Avraham Travers, James R Whittle, Sarah-Jane Dawson, Belinda Yeo, Jane E Visvader, Catherine Oakman, Geoffrey J Lindeman. PALVEN: A phase 1b study of palbociclib, letrozole and venetoclax in estrogen receptor, BCL2-positive metastatic breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr OT-27-01.

Abstract PS10-51: TAA013 a trastuzumab antibody drug conjugate phase I dose escalation study in recurrent her2 positive breast cancer

Abstract Background: A phase 1 dose escalation study of TAA013, an antibody drug conjugate linking trastuzumab to a cytotoxic small molecule, DM1, through an SMCC linker, in previously treated recurrent Her2 positive breast cancer patients. Material and Methods: This phase I study follows the traditional 3+3 design, dosing started at 0.6mg/kg, followed by 1.2, 2.4, 3.6, 4.8mg/kg, one intravenous infusion was given every 3 weeks, the initial infusion had to be over 90 minutes, infusion times were later shortened if treatment was well tolerated. The subsequent recommended dose would be expanded to include at least 10 patients. Patients were observed for dose-limiting toxicity (DLT) during a 21-day DLT observation period. Toxicities were graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events v5.0. Maximum-tolerated dose (MTD) was defined as the highest dose level that resulted in a DLT in no more than 1 of 6 patients. Study endpoints included safety and tolerability, pharmacokinetic and immunogenicity parameter evaluation, with preliminary evaluation of efficacy. Results: The study enrolled 22 female patients with histologically confirmed Her-2 positive metastatic breast cancer, median age of 50yrs (25-67), median time from initial diagnosis to TAA013 dosing was 39 months (5-99), median prior treatment regimen was 4 (2-10), all had received trastuzumab for a mean of 8.2 months (2-10), alone or in combination with chemotherapy, other prior Her2 targeting drugs given included pertuzumab (2), lapatinib (7), and pyrotinib (8). All patients received at least 2 (median of 6 infusions, range of 1-15) infusions, except for the last 4.8mg/kg patient, but all patients passed the dose limiting toxicity (DLT) observation period of 21 days. There were no dose limiting toxicities, no serious adverse events, nor that resulting in mortality, the maximum tolerated dose was not reached. The most common treatment emergent adverse events (TEAE) included 9 (40.9%) grade 1-2 infusion reactions associated with fever(5) and/or chills(1), the reaction often abated in subsequent cycles. There were no grade 4 TEAE, but there were 3 grade 3 thrombocytopenia, one grade 3 neutropenia, and one grade 3 hyperbilirubinemia which all recovered for the patients to continue treatment, there was also one grade 3 dermatitis in a patient with a history of chronic dermatitis. Antibody drug antibodies were not detected emanating from the TAA013 therapy. Pharmacokinetic studies included evaluation of TAA013, trastuzumab and DM1. Preliminary efficacy evaluation in the 2.4-4.8mg/kg dosing group of heavily pretreated patients resulted in 2 partial responses, including patients who had previously received pyrotinib therapy. Conclusion: TAA013 is a Her2 targeting antibody drug conjugate that is safe and tolerable, with efficacy demonstrated in heavily pretreated Her2 positive breast cancer patients. Keywords: breast cancer, antibody drug conjugates, TAA013. Citation Format: J M Liu, Y M Yin, Hao Wu, W Li, X Huang, XX Li. TAA013 a trastuzumab antibody drug conjugate phase I dose escalation study in recurrent her2 positive breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS10-51.

Cael-101 Is Well-Tolerated in AL Amyloidosis Patients Receiving Concomitant Cyclophosphamide-Bortezomib-Dexamethasone (CyborD): A Phase 2 Dose-Finding Study (NCT04304144)

Immunoglobulin light Chain (AL) amyloidosis is the most common form of systemic amyloidosis, accounting for approximately 70% of the diagnosed cases in developed countries. There are no approved treatments for AL amyloidosis, and currently autologous stem cell transplants and/or chemotherapy targeted to eradicate the underlying plasma-cell dyscrasia (PCD) to stop the production of misfolded light chains are used. No therapies are available to remove existing amyloid deposits, improve and/or reverse organ dysfunction. CAEL-101 is a chimeric immunoglobulin G1 kappa isotype that reacts specifically with light chain fibrils, irrespective of their κ or λ isotype but, notably, not with the native forms. CAEL-101 was shown to bind to a cryptic epitope at the N-terminal of light chain proteins that adopt a non-native b-sheet structure, which is conserved in κ and λ mis-folded light chains. It is hypothesized that CAEL-101 will modify the disease course of AL amyloidosis by facilitating the removal of amyloid fibrils deposited in tissues. CAEL-101 was previously studied as monotherapy in an open label dose escalation Phase 1 study where it was shown to be safe, tolerable up to 500 mg/m2 and associated with an early organ response. No DLT were seen and the PK profile appeared not to reach linearity. The current multicenter, open-label, sequential cohort, dose-selection study of CAEL-101 in Mayo Stage I, II and IIIa AL amyloidosis patients was to define the safety and tolerability of CAEL-101 in combination with Cyclophosphamide-Bortezomib-Dexamethasone (CyBorD) as the standard of care (SOC) PCD therapy during a 27-day treatment period and to determine the recommended dose for the subsequent Phase 3 studies. Patients had measurable hematologic disease, as defined by at least one of:involved/uninvolved free light chain (FLC) difference (dFLC) > 5mg/dL orFLC >5mg/dL with abnormal ratio orserum protein electrophoresis (SPEP) m- spike > 0.5 g/dL Patients were seen in the clinic every week for 4 weeks to receive CAEL-101 2-HR IV infusions, and for safety and tolerability assessments. Subsequently, patients have been receiving CAEL-101 infusions approximately every other week. Actual dose was determined by patient body surface area in meters squared. When administered on the same day, CAEL-101 was administered first before CyBorD chemotherapy. The study employed a 3+3 dose escalation design, starting with a 500 mg/m2 dose. Patients were followed for dose-limiting toxicities (DLTs). The DLT observation period for the first cohort was through 14 days following the first infusion. For subsequent cohorts, this was through 27 days. At least 3 patients were enrolled in each dose cohort. Enrollment into a new cohort with the next higher dose of CAEL-101 did not begin until the DLT observation period had been completed for the last patient enrolled in the previous cohort, with further dosing cohorts at 750 and 1000 mg/m2. Safety assessment included vital signs, physical examinations, electrocardiograms (ECGs), clinical laboratory parameters (hematology, serum chemistry, urinalysis), and TEAEs. The pharmacokinetic (PK) profile of CAEL-101 was also assessed. The 13 patients averaging 65.2 years (range 47.6 to 79.6 years). The majority were male (76.9%), white (84.6%), and non-Hispanic (100%). Mayo staging I (7.7%), II (69.2%), and III (23.1%) reflected a wide range of disease severity in the patients enrolled. All patients were treated successfully through their 4th dose, the highest (1000 mg/m2) cohort enrolling 6 patients. No DLT was observed, and CAEL-101 was well-tolerated by all patients. The most common TEAEs were diarrhea and nausea (each 30.8%). Dose-normalized PK concentrations were best described by a linear two-compartment model, with terminal half-life of 28 days. This study demonstrated that CAEL-101 at doses up to 1000 mg/m2, given with CyBorD, was well-tolerated in the AL amyloidosis population. Two Phase 3 efficacy/safety studies, one enrolling Mayo Stage IIIa and the other Stage IIIb patients, have been initiated, and based on the findings from this Phase 2 study, the 1000 mg/m2 dose of CAEL-101 is being used for treatment in those studies. Figure 1 Disclosures Valent: Takeda Pharmaceuticals: Other: Teaching, Speakers Bureau; Celgene: Other: Teaching, Speakers Bureau; Amgen Inc.: Other: Teaching, Speakers Bureau. Silowsky:Caelum Biosciences: Current Employment, Current equity holder in private company. Kurman:Caelum Biosciences: Consultancy. Daniel:Caelum Biosciences: Current Employment, Current equity holder in private company. Jobes:Caelum Biosciences: Current Employment, Current equity holder in private company. Harnett:Caelum Biosciences: Consultancy, Current equity holder in private company. Ziola:Caelum Biosciences: Consultancy. Roviwong:Caelum Biosciences: Current Employment, Current equity holder in private company. Spector:Caelum Biosciences: Current Employment, Current equity holder in private company. Sobolov:Caelum Biosciences: Current Employment, Current equity holder in private company.

Phase 2 Study of the Combination of Daratumumab, Ixazomib, Pomalidomide, and Dexamethasone As Salvage Therapy in Relapsed/Refractory Multiple Myeloma: Stage I Results

Background: Triplet combination regimens have been widely accepted as the standard of care for the management of multiple myeloma (MM) due to improved outcomes as compared to doublet regimens. The combination of daratumumab, pomalidomide, and dexamethasone (DPd) has previously demonstrated deep and durable responses including high rates of minimal residual disease (MRD) negativity in patients with relapsed/refractory (R/R) MM. Quadruplet regimens may further improve these outcomes. We report preliminary findings from an ongoing phase 2 multi-center trial of the addition of ixazomib to DPd (DIPd) in patients with R/R MM. Methods: We are conducting a prospective, multi-center, open-label, single-arm phase 2 study to determine the efficacy and safety of DIPd as salvage therapy in R/R MM. A Simon's optimal 2-stage design includes a safety run-in period at the beginning of Stage 1 where the first 6 patients are enrolled for toxicity assessment. If ≤1 patient experiences any DLT, the study continues to accrue more Stage 1 patients. Key secondary endpoints include progression-free survival (PFS), overall survival (OS) and MRD-negativity rates. Eligible patients may have received ≥1 and ≤3 prior lines of therapy, have had no prior exposure to daratumumab or ixazomib, are lenalidomide refractory, and may have not progressed on prior pomalidomide. The first six patients were treated in a safety run-in with daratumumab 16mg/kg IV weekly x 8 doses, biweekly x 8 doses, then monthly, pomalidomide 4mg orally daily on days 1-21 of a 28-day cycle, ixazomib 4mg orally daily on days 1,8,15 every 28 days, and dexamethasone 20-40mg weekly. Patients continued therapy until disease progression, intolerability or preference. Dose-limiting toxicities (DLT) were defined as grade 3-4 hematologic adverse events (AE) or any AE that required a dose modification of pomalidomide or ixazomib at the lowest dose levels on a dose de-escalation plan. An interim safety review is being performed after the enrollment and completion of the DLT observation period for the 14 planned patients in stage I. An interim efficacy analysis was also planned after all patients had completed 3 months of therapy. Minimal residual disease assessments are being performed by EuroFlow for patients in VGPR or suspected CR. Pharmacodynamic changes in patients' tumor microenvironments were established by custom panel mass cytometry to include T-cell memory and activated subpopulations, B-cell content, NK-cell subpopulations as well as MDSCs, Tregs and T-exhaustive markers, monocytes and dendritic cells. Results: At the time of this analysis, all 14 patients have enrolled and started treatment as part of stage I of the trial. Patients had a median age of 61 (range 52-65) and median number of 1 prior line of therapy (range 1-3). All patients were refractory to lenalidomide and all were pomalidomide naïve. In the safety run-in, all 6 patients experienced ≥ grade 3 neutropenia, and per DSMB recommendation, the starting doses of pomalidomide and ixazomib were both reduced to 3mg for the subsequent 8 patients in stage 1. Common AEs included neutropenia, thrombocytopenia, and upper respiratory infection. Grade 3-4 AEs were predominantly hematologic, including neutropenia and thrombocytopenia. One patient had a grade 3 infusion-related reaction (IRR) with daratumumab administration. No DLTs have occurred. After median follow up of 4.1 months (range 1-22), all 14 patients were evaluable for efficacy. At the time of data analysis, the overall response rate to date is 85%, and the best responses include: 5 (36%) stringent complete response; 1 (7%) very good partial response; 5 (36%) partial responses; and 3 (21%) patients with stable disease. Six (42%) patients are off study treatment: 3 due to disease progression, 1 to undergo salvage autologous SCT, and 2 due to toxicity related to treatment (IRR and upper respiratory infection). MRD and pharmacodynamic data will be presented at ASH. Conclusion: The quadruplet regimen DIPd in patients with R/R MM is a well-tolerated combination and has shown early safety and promising efficacy in the first 14 patients enrolled to stage 1 of the trial. A pre-planned interim efficacy analysis is ongoing prior to future enrollment in stage 2 at multiple sites within the University of California Hematologic Malignancies Consortium. Disclosures Costello: Celgene: Honoraria, Research Funding; Janssen: Research Funding; Poseida Therapeutics: Research Funding; Takeda: Consultancy, Honoraria, Research Funding. Wieduwilt:Daiichi Sankyo: Membership on an entity's Board of Directors or advisory committees; Shire: Research Funding; Macrogeneics: Research Funding; Amgen: Research Funding; Leadiant: Research Funding; Merck: Research Funding; Reata Pharmaceuticals: Current equity holder in publicly-traded company. Shah:GSK, Amgen, Indapta Therapeutics, Sanofi, BMS, CareDx, Kite, Karyopharm: Consultancy; BMS, Janssen, Bluebird Bio, Sutro Biopharma, Teneobio, Poseida, Nektar: Research Funding.