Iga Sienczylo

Abstract Background: B cell maturation antigen (BCMA) has recently emerged as a promising candidate antigen for therapeutic targeting in multiple myeloma (MM), with several targeted agents in clinical studies including antibody-drug conjugates and bispecific T cell engagers as well as CAR T cells. The Antibody-Coupled T cell Receptor (ACTR) platform is a universal, engineered autologous T cell therapy developed to mediate anti-tumor activity in combination with tumor-targeting antibodies. The ACTR construct is composed of the ectodomain of CD16 fused to intracellular co-stimulatory and CD3ζ signaling domains (Kudo et al., Cancer Res. 2014), which allow ACTR T cells to exert antibody-dependent cell-mediated cytotoxicity, a function otherwise physiologically limited to CD16-expressing natural killer cells and macrophages. ACTR087 expresses a 4-1BB-containing receptor and has been evaluated in combination with rituximab in subjects with relapsed or refractory (R/R) CD20+ B cell lymphoma as previously reported (Akard et al., Blood 2017). SEA-BCMA is a novel, humanized non-fucosylated anti-BCMA IgG1 antibody that has been demonstrated pre-clinically to bind to ACTR087 T cells to mediate ACTR T cell activation, cytotoxicity, cytokine release, and proliferation in the presence of BCMA-expressing MM cell lines. These functional activities were demonstrated to be BCMA-specific and SEA-BCMA dose-dependent (Cheema et al., AACR 2017). Here we present preliminary findings from the first 2 single-subject cohorts of the ATTCK-17-01 study (NCT03266692), an ongoing Phase 1 study of ACTR087 in combination with the first-in-human administration of SEA-BCMA. Methods: ATTCK-17-01 is a multicenter, Phase 1, dose-escalation study of ACTR087 in combination with SEA-BCMA. The primary objectives are to characterize the safety and to determine the recommended Phase 2 dose of ACTR087 in combination with SEA-BCMA in subjects with R/R MM. The secondary objectives include evaluation of anti-myeloma activity, ACTR T cell persistence, cytokines, and SEA-BCMA pharmacokinetics (PK); exploratory objectives include the anti-myeloma activity of SEA-BCMA alone. Subjects must have measurable disease and must have received at least 3 prior lines of therapy including treatment with a proteasome inhibitor and an immunomodulatory agent, and hematopoietic stem cell transplant (HSCT) for HSCT-eligible subjects. BCMA expression on MM cells was not a condition of eligibility. Dose escalation of the 2 investigational agents, ACTR087 and SEA-BCMA, is determined according to adaptive design principles. After study enrollment and leukapheresis, subjects receive SEA-BCMA by IV infusion once every 3 weeks until disease progression or treatment discontinuation. After the third dose of SEA-BCMA and lymphodepleting chemotherapy (cyclophosphamide 300 mg/m2 and fludarabine 30 mg/m2, each daily for 3 days), subjects receive a single dose of ACTR087. Results: Two subjects enrolled and received ACTR087 at the first dose level in combination with the first 2 dose levels of SEA-BCMA. First-in-human dosing of SEA-BCMA was well tolerated, with no reported SEA-BCMA-related adverse events (AEs) or dose-limiting toxicities (DLTs). Following ACTR087 infusion, ACTR+ T cells were detectable in the peripheral blood and demonstrated expansion post-infusion. No DLTs were observed with the combination of ACTR087 and SEA-BCMA in the first 2 cohorts. Grade 3 or higher treatment-emergent AEs experienced by at least 1 subject, regardless of causality assessment, include cytopenias, increased ALT, and bone pain. Conclusions: ACTR087 in combination with SEA-BCMA was well tolerated in the first 2 subjects treated, with no DLTs or AEs leading to treatment discontinuation. These results support the continued dose escalation of ACTR087 in combination with SEA-BCMA. Enrollment in Cohort 3 is ongoing. Updated data, including SEA-BCMA PK, biomarkers, and preliminary Cohort 3 data, will be presented. Disclosures Holmes: Unum: Research Funding; Seattle Genetics: Research Funding, Speakers Bureau; Novartis: Research Funding; Genentech: Research Funding; Celgene: Research Funding; Rigel: Consultancy; Gilead: Consultancy, Research Funding, Speakers Bureau; Bayer: Consultancy. Hari:Kite Pharma: Consultancy, Honoraria; Janssen: Honoraria; Celgene: Consultancy, Honoraria, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Amgen Inc.: Research Funding; Takeda: Consultancy, Honoraria, Research Funding; Spectrum: Consultancy, Research Funding; Sanofi: Honoraria, Research Funding. Sachs:Unum Therapeutics Inc.: Employment. Exter:Unum Therapeutics Inc.: Employment. Ranger:Unum Therapeutics Inc.: Employment. Cheema:Unum Therapeutics Inc.: Employment. Sienczylo:Unum Therapeutics Inc.: Employment. O'Meara:Seattle Genetics: Employment, Equity Ownership. Sussman:Seattle Genetics: Employment. Akard:Gilead: Speakers Bureau; Celgene: Speakers Bureau; Takeda: Speakers Bureau; Novartis: Speakers Bureau; Bristol-Myers Squibb: Speakers Bureau.

Abstract Background: RTX-240 is an allogeneic cellular therapy genetically engineered to express high copy numbers of trimeric 4-1BBL and IL-15/IL-15Rα fusion proteins on the RBC surface membrane. RTX-240 is designed to activate and expand CD8+ memory T cells and NK cells and is restricted to the normal biodistribution of red blood cells to mitigate toxicity. Safety, pharmacodynamic (PD) effects, pharmacokinetics (PK) and preliminary efficacy of RTX-240 were assessed in a Phase 1 study of pts with solid tumors. Methods: Pts with relapsed/refractory solid tumors not eligible for standard therapy were treated with monotherapy RTX-240 in 10 cohorts utilizing 6 dose levels (1x108-5x1010 cells per dose) and 4 different schedules until disease progression or unacceptable toxicity. Peripheral blood and tumor tissue were collected at baseline and on-treatment. Results: As of Dec 3, 2021, 30 pts with solid tumors (median age 58 yr, range 23-80, 17 males, 20 ECOG 1), were treated with single agent RTX-240. Pts had previously received a median of 3 therapies (range, 1-9); 21 pts had received prior PD-1/PD-L1 inhibitor (i) therapy. Common tumor types included NSCLC (n=7), melanoma (n=7), colorectal/lower GI (n=4) and RCC (n=3). Per RECIST v1.1, a confirmed partial response (PR) was observed in 1 pt with anal carcinoma and an unconfirmed PR in a uveal melanoma, both of whom had been previously treated with a PD-1. Disease control (PR or stable disease > 12 weeks) occurred in 11/30 pts (37%), of which 7 had received a prior PD-1 for a median of 8 months. Peripheral blood PD studies demonstrate activation, expansion, and cytotoxic potential (GzB) of both NK and memory CD8+ T cells. Every pt with evaluable samples (n=29) had an increase in at least one of the activation or expansion parameters, and the majority had an increase in all. There was also a clear dose response effect in NK cell numbers and trends in other PD markers. Immune activation was observed by increases in plasma IFN-γ in a subset of patients. On-treatment biopsies in a subset (3/5) of evaluable pts show infiltration of NK and/or T cells into the tumor microenvironment (TME) after RTX-240 dosing. No DLTs or related grade (Gr)>3 AEs were seen. The most common treatment-related AEs (Gr 1-2) were fatigue (n = 6); chills, nausea, decrease in appetite, arthralgia (n =3); and fever, myalgia, dysgeusia, and hyperhidrosis (n=2). Additional Gr 2 irAEs include pneumonitis, adrenal insufficiency, hypothyroidism, and worsening transaminitis. Conclusions: RTX-240 is well tolerated at all tested doses, schedules and routes. The drug leads to activation, expansion and trafficking of two target cells (memory CD8+ T cells and NK cells) into the TME, exhibits a clear dose response effect with NK cells and demonstrates preliminary evidence of anti-tumor activity. Dose escalation continues and a PD-1 inhibitor combination arm is also enrolling. Citation Format: Omid Hamid, Melissa L. Johnson, Jason Luke, Richard T. Maziarz, Jamie Merchan, Emerson E. Lim, Sandip P. Patel, Geoffrey M. Kuesters, Iga Sienczylo, Gilad Gordon, Karen Campbell, Kristin Horton, Laurence Turka, Alexander I. Spira. Phase 1 Trial of RTX-240, allogeneic red blood cells engineered to express 4-1BBL and trans-presented IL-15, in patients (Pts) 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 CT187.

Patients with non-small cell lung cancer (NSCLC) with loss of the tumor suppressor gene STK11 are resistant to immune checkpoint therapies like anti-PD-1. In this study, we conducted an in vivo CRISPR screen that identified histone deacetylase 1 as a target to reverse anti-PD-1 resistance driven by loss of STK11 and developed TNG260, a potent small-molecule inhibitor of the CoREST complex with selectivity exceeding previously generated inhibitors in this class in preclinical studies. Treatment with TNG260 led to increased expression of immunomodulatory genes in STK11-deficient cancer cells. When combined with anti-PD-1, TNG260 induced immune-mediated stasis and/or regression in STK11-deficient syngeneic tumor models and autochthonous NSCLC models. In the tumors of patients with STK11-deficient cancers in a clinical trial (NCT05887492), treatment with a combination of TNG260 and pembrolizumab increased intratumoral histone acetylation, PD-L1 tumor proportion scores, and T-cell infiltration into the tumor microenvironment. This study illustrates a promising treatment strategy for addressing immune evasion in patients with STK11-mutant NSCLC. SIGNIFICANCE: Targeting CoREST with TNG260 sensitizes STK11-deficient non-small cell lung cancer to anti-PD-1 immunotherapy, offering a potential treatment for patients not served by existing therapies. See related commentary by Lin and Shen, p. 3821.

Abstract Short title: RTX-240 phase 1 in solid tumorsA phase 1 trial of RTX-240, an allogeneic engineered red blood cell with cell -surface expression of 4-1BBL and trans-presented IL-15, in patients with advanced solid tumorsBackground: T cell checkpoint inhibition has revolutionized the treatment of cancer, however the key challenge in cancer immunotherapy is the development of resistant disease. Immune agonists and cytokines are promising approaches, but have shown limited success in the clinic. RTX-240 is an allogeneic cellular therapy genetically engineered to express high-copy numbers of trimeric 4-1BBL and IL-15/IL-15R fusion proteins on the cell surface. RTX-240 is designed to activate and expand CD8+ memory T cells and NK cells, and is restricted to the normal biodistribution of red blood cells to mitigate toxicity. Safety, pharmacodynamic (PD) effects, pharmacokinetics and preliminary efficacy of RTX-240 were assessed in a phase 1 study in patients (pts) with solid tumors. Methods: Pts with relapsed/refractory solid tumors not eligible for standard therapy were treated in dose escalating cohorts with RTX-240 Q4 or Q6W until disease progression or unacceptable toxicity. An exploratory cohort of IV and intratumoral (IT) dosing was enrolled (QW IV and IT x3 in cycle 1 and Q4W IV in subsequent cycles). Results: As of 11 Dec 2020, 14 pts (median age 55) were treated across 4 dose levels (1x108 to 1x1010 cells) administered IV or IV/IT. Pts had received a median of 3.5 therapies (range, 1-10); 10 pts had received prior PD-1/PD-L1 inhibitor therapy. Common tumor types include colorectal or other GI cancers (n=5) and melanoma (n=5). No patients experienced DLTs and no related grade (gr) >3 AE were observed. The most common related AE (gr 1-2) were fatigue (4 pts); chills, decreased appetite, arthralgia (3 pts each); and fever, myalgia, dysgeusia, nausea and hyperhidrosis (2 pts each). Additional irAE include gr 2 pneumonitis (n=1) and gr 1 elevated ALT/AST (n=1); the majority of irAE were observed in cycle 2 and beyond. RTX-240 was detected at the end of infusion sample in a dose dependent manner. Five pts (Q4W IV dosing) were evaluable for response by RECIST v1.1. A confirmed partial response (PR) was observed in 1 pt with anal cancer. Disease control, including stable disease or PR, occurred in 4/5 pts. PD studies in peripheral blood from all pts indicated increased numbers of NK cells in 12/14 pts (change from baseline, range 1.1-3 fold) and memory CD8+ T cells in 10/14 pts (change from baseline, range 1.2-3.3 fold). Activation of both NK and memory CD8+ T cells was observed by increased HLA-DR expression in 11/14 and 14/14 pts, respectively. Optional on-treatment biopsies are collected and preliminary data in one pt suggests infiltration of activated NK and T cells into the tumor microenvironment following dosing with RTX-240. Conclusions: RTX-240 is tolerable and leads to activation, expansion and trafficking of memory CD8+ T cells and NK cells, with preliminary evidence of anti-tumor activity. Exploration of the dose and schedule are ongoing in this study (NCT04372706). Citation Format: Omid Hamid, Jason Luke, Alexander Spira, Geoffrey M. Kuesters, Iga Sienczylo, Gilad Gordon, Melissa L. Johnson. A phase 1 trial of RTX-240, an allogeneic engineered red blood cell with cell -surface expression of 4-1BBL and trans-presented IL-15, in patients with advanced solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT141.

<div>Abstract<p>Patients with non–small cell lung cancer (NSCLC) with loss of the tumor suppressor gene <i>STK11</i> are resistant to immune checkpoint therapies like anti–PD-1. In this study, we conducted an <i>in vivo</i> CRISPR screen that identified histone deacetylase 1 as a target to reverse anti–PD-1 resistance driven by loss of <i>STK11</i> and developed TNG260, a potent small-molecule inhibitor of the CoREST complex with selectivity exceeding previously generated inhibitors in this class in preclinical studies. Treatment with TNG260 led to increased expression of immunomodulatory genes in <i>STK11</i>-deficient cancer cells. When combined with anti–PD-1, TNG260 induced immune-mediated stasis and/or regression in <i>STK11</i>-deficient syngeneic tumor models and autochthonous NSCLC models. In the tumors of patients with <i>STK11</i>-deficient cancers in a clinical trial (NCT05887492), treatment with a combination of TNG260 and pembrolizumab increased intratumoral histone acetylation, PD-L1 tumor proportion scores, and T-cell infiltration into the tumor microenvironment. This study illustrates a promising treatment strategy for addressing immune evasion in patients with <i>STK11</i>-mutant NSCLC.</p>Significance:<p>Targeting CoREST with TNG260 sensitizes <i>STK11</i>-deficient non-small cell lung cancer to anti-PD-1 immunotherapy, offering a potential treatment for patients not served by existing therapies.</p><p><a href="https://aacrjournals.org/cancerres/article-abstract/doi/10.1158/0008-5472.CAN-25-4003" target="_blank"><i>See related commentary by Lin and Shen, p. 3821</i></a></p></div>