Select Solid Tumors Research Articles

A phase 1/2 study of RTX-224, an engineered red blood cell expressing 4-1BB ligand and membrane-bound IL-12, for the treatment of patients with select advanced solid tumors.

TPS2680 Background: RTX-224 is a genetically engineered off-the-shelf, allogeneic red blood cell that expresses the costimulatory molecule 4-1BB ligand (4-1BBL) and cytokine interleukin-12 (IL-12) on the cell surface. The use of 4-1BB and IL-12 agonists for cancer immunotherapy has been limited due to systemic toxicities. Unlike agonist antibodies and recombinant cytokines, which are distributed systemically, Red Cell Therapeutics, such as RTX-224, are restricted to the vasculature and spleen, which may limit toxicities previously observed with agonist 4-1BB monoclonal antibodies and recombinant IL-12. RTX-224 is designed to be a broad immune agonist of both adaptive and innate responses that activates and expands effector and memory CD8+ and CD4+ T cells, cytotoxic natural killer (NK) cells and produces inflammatory cytokines and chemokines, leading to enhanced antigen presentation. In preclinical studies, the combined activation of both adaptive and innate immune responses by the murine surrogate of RTX-224 led to antitumor activity while the restricted biodistribution improved the safety profile. Methods: The RTX-224-01 study is a Phase 1/2, first-in-human, multi-center, dose-escalation and expansion study of RTX-224 in patients with relapsed or refractory urothelial cancer, squamous cell carcinoma of the head and neck, non-small cell lung cancer, triple negative breast cancer and cutaneous melanoma. Safety, tolerability, pharmacokinetics and pharmacodynamics and anti-tumor activity of RTX-224 will be assessed. Approximately 28 patients will be enrolled across dose level cohorts to identify the recommended Phase 2 dose (RP2D). The starting dose is 100 million (1x108) cells administered intravenously every 3 weeks (Q3W) and the dose will be escalated by half-log increments following a Bayesian logarithmic regression model (BLRM) with overdose control. Following RP2D selection, each of the 5 expansion cohorts will enroll approximately 20 patients. Pharmacodynamic and exploratory biomarker studies correlative to clinical response will be evaluated on peripheral blood and paired tumor biopsies. Multiple technologies will be employed to profile the innate and adaptive responses following RTX-224 treatment. The study is open and enrolling patients in Phase 1. Clinical trial information: NCT05219578.

BOXR1030, an anti-GPC3 CAR with exogenous GOT2 expression, shows enhanced T cell metabolism and improved anti-cell line derived tumor xenograft activity.

PurposeThe solid tumor microenvironment (TME) drives T cell dysfunction and inhibits the effectiveness of immunotherapies such as chimeric antigen receptor-based T cell (CAR T) cells. Early data has shown that modulation of T cell metabolism can improve intratumoral T cell function in preclinical models.Experimental designWe evaluated GPC3 expression in human normal and tumor tissue specimens. We developed and evaluated BOXR1030, a novel CAR T therapeutic co-expressing glypican-3 (GPC3)-targeted CAR and exogenous glutamic-oxaloacetic transaminase 2 (GOT2) in terms of CAR T cell function both in vitro and in vivo.ResultsCell surface expression of tumor antigen GPC3 was observed by immunohistochemical staining in tumor biopsies from hepatocellular carcinoma, liposarcoma, squamous lung cancer, and Merkel cell carcinoma patients. Compared to control GPC3 CAR alone, BOXR1030 (GPC3-targeted CAR T cell that co-expressed GOT2) demonstrated superior in vivo efficacy in aggressive solid tumor xenograft models, and showed favorable attributes in vitro including an enhanced cytokine production profile, a less-differentiated T cell phenotype with lower expression of stress and exhaustion markers, an enhanced metabolic profile and increased proliferation in TME-like conditions.ConclusionsTogether, these results demonstrated that co-expression of GOT2 can substantially improve the overall antitumor activity of CAR T cells by inducing broad changes in cellular function and phenotype. These data show that BOXR1030 is an attractive approach to targeting select solid tumors. To this end, BOXR1030 will be explored in the clinic to assess safety, dose-finding, and preliminary efficacy (NCT05120271).

Graft-Versus-Solid-Tumor Effect: From Hematopoietic Stem Cell Transplantation to Adoptive Cell Therapies.

After allogeneic hematopoietic stem cell transplantation (HSCT), donor lymphocytes may contribute to the regression of hematological malignancies and select solid tumors, a phenomenon referred to as the graft-versus-tumor effect (GVT). However, this immunologic reaction is frequently limited by either poor specificity resulting in graft-versus-host disease or the frequency of tumor-specific T cells being too low to induce a complete and sustained anti-tumor response. Over the past 2 decades, it has become clear that the driver of GVT following allogeneic HSCT is T-cell-mediated recognition of antigens presented on tumor cells. With that regard, even though the excitement for using HSCT in solid tumors has declined, clinical trials of HSCT in solid tumors provided proof of concept and valuable insights leading to the discovery of tumor antigens and the development of targeted adoptive cell therapies for cancer. In this article, we review the results of clinical trials of allogeneic HSCT in solid tumors. We focus on lessons learned from correlative studies of these trials that hold the potential for the creation of tumor-specific immunotherapies with greater efficacy and safety for the treatment of malignancies.

What's new in molecular genetic pathology 2022: immune checkpoint inhibitor biomarkers and select solid tumors.

Predictive biomarker testing plays a critical role in targeted immuno-oncology, including the use of immune checkpoint inhibitors (ICI) for various solid tumors. Molecular advancements in cancers of the breast, kidney and brain have continued to propel tumor classification and precision therapy.

Alignment of health plan coverage policies for somatic multigene panel testing with clinical guidelines in select solid tumors.

Aim: Commercial plan coverage policies for multigene panel testsmay vary and could result in geographic variation in coverage due to the fragmented nature of the commercial insurance market. This study aimed to characterize the alignment of multigene panel tests coverage policies to that of clinical guidelines, overall and by state. Materials &methods: We reviewed NCCN Guidelines® for fourtumors. Public coverage policies were identified via web search. Payer policies included those with the largest or second largest number of commercial lives in each state. Policies were classified as 'more restrictive'or 'consistent'with the guidelines. Results: Of 38 plans/policies reviewed, 71% were classified as 'more restrictive'than the guidelines, with variation in the number of commercial lives by state. Among these, 52% restricted on panel size and 63% restricted in all or select tumors. Conclusion: Most coverage policies were more restrictive. Clinical guideline clarity and state policies may improve alignment to guidelines and geographic variations.

A phase 2, multicenter, open-label study evaluating trastuzumab deruxtecan (T-DXd) for the treatment of select human epidermal growth factor receptor 2 (HER2)-expressing solid tumors (DESTINY-PanTumor02).

TPS623 Background: Human epidermal growth factor receptor 2 (HER2) is an established therapeutic target in both breast and gastric cancer. However, HER2-targeting therapies are not approved beyond these malignancies despite a high prevalence of HER2 expression across cancers of epithelial origin. Trastuzumab deruxtecan (T-DXd) is an antibody-drug conjugate consisting of an anti-HER2 antibody, a cleavable tetrapeptide-based linker, and a topoisomerase I inhibitor payload. In a cohort of pretreated patients with multiple HER2-expressing tumors, T-DXd demonstrated promising antitumor activity, with an investigator-assessed confirmed objective response rate of 40.9% (9 of 22 patients) and median progression-free survival of 11.1 months (95% CI, 5.4-20.5 months; Tsurutani J, et al. Cancer Discov. 2020;10:688-701). Here we describe the phase 2 DESTINY-PanTumor02 trial evaluating T-DXd in patients with select HER2-expressing solid tumors. Methods: DESTINY-PanTumor02 (NCT04482309) is an open-label, multicenter, multicohort, phase 2 study evaluating T-DXd for the treatment of patients with select HER2-expressing locally advanced, unresectable, or metastatic tumors. The study will consist of 7 cohorts of patients (n≈40 each) with urothelial bladder, biliary tract, cervical, endometrial, ovarian, pancreatic, or rare tumors (tumors excluding those in the other cohorts and breast, gastric, colorectal, and non-small cell lung cancer). Patients are required to have disease progression following ≥1 prior systemic treatment for advanced or metastatic disease or have no satisfactory alternative treatment options. Prior HER2-targeting therapy is allowed. The primary endpoint is investigator-assessed confirmed objective response rate per Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1. Secondary endpoints include duration of response, disease control rate, progression-free survival (all per investigator assessment according to RECIST 1.1), overall survival, safety, pharmacokinetics, and immunogenicity. Previously presented at the ESMO Congress 2021, FPN: 1869 TiP, Meric-Bernstam et al. Reused with permission. Clinical trial information: NCT04482309.

Hepatology Highlights.

Potential conflict of interest: Nothing to report. DR CELLS ROUND UP NEW TUBES Ryan Watkins1 and Sumera I. Ilyas2 Liver injury increases ductular reaction (DR) and contributes to the wound‐healing process, but how DR cells affect the local microenvironment is not fully understood. The slit guidance ligand 2 (SLIT2)/roundabout guidance receptor 1 (ROBO1) axis promotes angiogenesis in select solid tumors, but whether this signaling pathway induces intrahepatic angiogenesis in acute or chronic liver injury is unknown. Using murine liver injury models and human liver specimens, Coll et al. elucidate that SLIT2 secreted by DR cells binds ROBO1 on new endothelial cells and promotes neoangiogenesis in chronic liver injury. Administering mice a diet enriched in 3,5‐diethoxycarbonyl‐1,4‐dihydrocollidin or a choline‐deficient, ethionine‐supplemented (CDE) diet results in DR expansion. This was paralleled by increased neoangiogenesis, which is diminished in mice heterozygous for ROBO1/2. Similar findings were demonstrated in a cohort of patients with alcohol‐associated liver disease (ARLD). Interestingly, SLIT2 serum levels correlated with disease severity in patients with alcohol‐associated hepatitis. In a separate cohort of patients with NAFLD or HBV infected and without cirrhosis, liver DR markers correlated with SLIT2‐ROBO1 signaling, indicating that this response is not specific to ARLD. Altogether, these findings suggest that intrahepatic angiogenesis mediated by DR cell SLIT2 expression in response to chronic liver injury is an important and clinically relevant process in liver repair. (Hepatology 2022;75:353‐69). THE CHOLESTATIC CONUNDRUM Daniel D. Penrice2 and Sumera I. Ilyas2 Patients with intestinal failure related to short bowel syndrome or other causes are often on prolonged parenteral nutrition (PN) and thus are at risk of developing PN‐associated cholestasis (PNAC). PNAC is characterized by persistent hyperbilirubinemia during PN administration. Although the development of PNAC is multifactorial, phytosterols present in the PN solution have been implicated in the process and shown to suppress hepatocyte farnesoid X receptor (FXR) signaling. FXR is activated by bile acids and plays a major regulatory role in the liver. El Kasmi et al. used a murine model of PNAC using the combination of dextran sodium sulfate–induced intestinal injury and PN infusion. In this model, the FXR agonist, GW4064, activated FXR signaling with restoration of bile acid transporter expression and normalization of the serum bile acid profile. Moreover, FXR agonism reduced hepatic macrophage infiltration with a consequent reduction in hepatic inflammation and cholestasis. These findings suggest that FXR agonists added to PN are a potential therapeutic strategy to decrease the incidence of PNAC. (Hepatology 2022;75:252‐66). CHECK THE TIME: IS CCA READY FOR IMMUNOTHERAPY? Caitlin B. Conboy3 and Sumera I. Ilyas2 Cancer initiation and progression are facilitated by an immunosuppressive tumor immune microenvironment (TIME), characterized by suppressive immune cells and immune checkpoint molecules. Immune checkpoint inhibitors (ICI) have transformed the treatment of many cancers, yet their efficacy in cholangiocarcinoma (CCA) is limited to date. Carapeto et al. sought to identify which immune checkpoints are salient in CCA and how their expression correlates with leukocyte infiltration, underlying genetic drivers, and patient survival. The investigators focused on a subset of patients with resected, fluke‐negative, and predominantly HBV/HCV‐negative intrahepatic CCA (N = 96). Using immunohistochemistry profiling, they identified that both immune cell (CD4+/CD8+ T cells, macrophages) and checkpoint molecule expression (lymphocyte activating 3 [LAG3], OX40, programmed cell death 1 [PD‐1], and T‐cell immunoglobulin and mucin‐domain containing 3) were decreased in the tumor center compared to the invasive margin. Only a small subset of patients had a “hot” TIME. In contrast, a signature of low T‐cell infiltration and high PD‐1 or LAG3 expression was associated with poor overall survival. Correlation of immune checkpoints and genetic mutations identified an association of BRCA1‐associated protein 1 loss‐of‐function mutation with increased expression of the immune checkpoint, B7H4. Tumors with a “cold” TIME have been inherently resistant to ICI therapy. However, broad profiling of the CCA TIME may facilitate development of, and predict response to, novel immunotherapy approaches. (Hepatology 2022;75:297‐308). ALCOHOL AND OBESITY ADDITIVELY INCREASE CIRRHOSIS RISK Gustavo Ayares4 and Juan Pablo Arab4 The relationship between alcohol and obesity on the risk of cirrhosis morbidity remains unclear given that some studies have demonstrated a reduction and others have demonstrated an additive or supra‐additive effect. To assess this interaction in a large population‐based study, Innes et al. used data from the UKB (United Kingdom Biobank) study and examined the relationship between body mass index (BMI) and alcohol intake on cirrhosis morbidity, which was defined by first‐time hospital admission for cirrhosis. Incidence of cirrhosis morbidity increased with alcohol intake and BMI independently. Excess cumulative incidence was highest for obese harmful drinkers (1.83%; 95% CI, 1.46–2.20), compared to harmful drinking alone (1.22%; 95% CI, 0.89–1.55), and obesity alone (0.4%; 95% CI, 0.34–0.46). These findings are consistent with previous studies that have demonstrated an additive effect of alcohol and BMI on the risk of liver disease. (Hepatology 2022;75:369‐78).

Abstract P042: Phase I/II first-in-human study of TT-10 (A2AB inhibitor) as a single agent in subjects with advanced selected solid tumors

Abstract Immunotherapy has emerged as a potent tool for cancer treatment by activating the immune system to recognize and attack cancer cells. Immune checkpoint blockage has shown notable clinical success in several malignancies such as advanced non-small cell lung cancer, melanoma, advanced kidney cancer and several other indications, as demonstrated with the approval of CTLA-4 and PD-1/PD-L1 checkpoint inhibitors. However, the efficacy of checkpoint inhibitors to date is limited to only a subset of patients, even within the same cancer type. Thus, the continued focus in the cancer immunotherapy field is to identify new immunosuppressive pathways that allow cancer cells to evade immune surveillance. One emerging pathway of interest is the purinergic pathway, in which adenosine is recognized as a key metabolic checkpoint, and high levels of extracellular adenosine have been evidenced to mediate profound tumor resistance. In this first-in-human Phase I/II study, we explore selective inhibition of the adenosine A2A receptor (A2AR) with TT-10, an oral immune-oncology agent, as a treatment option for subjects with select solid tumors. TT-10 is being evaluated as a single agent, in an open-label, non-randomized, multicenter, dose-escalation (phase 1) and dose-expansion (phase 2) study in subjects with renal cell cancer (RCC), castrate resistant prostate cancer (CRPC) and non-small cell lung cancer (NSCLC) (NCT# NCT04969315). Phase 1 (Cohort A) will explore ascending doses of TT-10, taken orally (10, 20, 50, 100, 200 mg, BID), utilizing a 3+3 design in 28-day cycles to identify the maximum tolerated dose (MTD) and/or recommended Phase 2 dose (R2PD). Enrollment will be open to all three indications. Phase 2 will begin once RP2D is determined and will enroll up to 60 subjects, with approximately 15 subjects per cohort (B.) RCC, (C.) CRPC, (D.) NSCLC (E.) Exploratory Tumor Biopsy). The primary objectives of this study are to evaluate the safety, tolerability, and MTD or the RP2D of TT-10 monotherapy. Secondary objectives are to obtain a preliminary estimate of efficacy, evaluate PK and anti-tumor activity of TT-10 monotherapy, with exploratory objectives inclusive of identification of candidate biomarkers and biomarkers that might predict response, as well as, exploring if adenosine signature and/or receptor expression in tumor tissue at baseline might predict response. Subjects must have locally advanced, recurrent or metastatic neoplastic disease that is not curable by currently available, failure to respond to standard therapy or for whom no appropriate therapies are available, and have a life expectancy of ≥ 3 months to be eligible for the trail. Select subjects that would like to participate in Cohort E.) Exploratory Tumor Biopsy must have an accessible tumor for pre and post dose biopsies. Enrollment of phase 1 is expected to start October 2021. Citation Format: Sushant Kumar, Kasim Mookhtiar, Desa Rae Pastore, Brian Schwartz, Vijay Reddy. Phase I/II first-in-human study of TT-10 (A2AB inhibitor) as a single agent in subjects with advanced selected solid tumors [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P042.

Abstract P237: PRT2527 is a potent and selective CDK9 inhibitor that demonstrates anti-cancer activity in preclinical models of hematological malignancies and solid tumors with MYC amplification

Abstract Cyclin-dependent kinase 9 (CDK9) is a master regulator of transcription that controls paused RNA polymerase II (RNAP2) release through phosphorylation of its carboxy-terminal domain, resulting in productive transcription elongation. CDK9 has been extensively studied as a potential target for cancer therapy in “transcriptionally addicted” tumors as transient inhibition of CDK9 primarily depletes proteins with short half-lives, such as the oncogenes MCL1 and MYC, making CDK9 a promising target in cancer. Here we show that PRT2527 is a potent and highly selective CDK9 inhibitor with moderate to high clearance that achieves optimal temporal target engagement and exhibits potent in vitro and in vivo activities. PRT2527 inhibited CDK9 enzymatic activity with an IC50 of 0.98 nM in a biochemical assay and showed high selectivity in a panel of kinases when tested at physiologically relevant 1 mM ATP concentration. In vitro, PRT2527 inhibited phosphorylation of Ser2RNAP2 in NCI-H929 cells with an IC50 of 54 nM, and an IC50 of 198 nM in a plasma assay to adjust for human plasma protein binding. Transient treatment of cells with PRT2527 inhibited pSer2RNAP2, depleted MCL1 and MYC proteins, and activated cleaved caspase-3 (CC3) in a concentration-dependent manner. In a proteomic profiling study, MCL1 was identified as one of the major down-regulated proteins following PRT2527 treatment. In a panel of hematological cancer cell lines representing B- and T-ALL, AML, and non-Hodgkin’s lymphoma (NHL), as well as subsets of sarcoma, prostate, adenoid cystic carcinoma (ACC), and non-small cell lung cancer (NSCLC) cell lines, PRT2527 treatment consistently led to a potent, concentration-dependent inhibition of proliferation. In a pharmacokinetic/pharmacodynamic (PK/PD) study, intravenous (IV) administration of PRT2527 achieved transient target engagement, depletion of MCL1 and MYC proteins, and induction of apoptosis in tumor tissue. This PK/PD correlation was successfully translated into in vivo efficacy in multiple models. Once weekly dosing of PRT2527 was well-tolerated and significantly inhibited tumor growth in various AML CDX models and induced tumor regressions in double-hit and triple-hit diffuse large B-cell lymphoma (DLBCL) CDX and PDX models carrying the MYC translocation. Combining PRT2527 with venetoclax achieved complete tumor regressions in a venetoclax resistant OCI-AML3 model. PRT2527 demonstrated potent ex vivo activity in PDX models of B-ALL and T-ALL, as well as various solid tumor PDX models with high levels of MYC amplification and overexpression, including pancreatic carcinoma, gastric and gastroesophageal carcinomas, NSCLC, and sarcoma. In vivo efficacy studies with once weekly IV administration of PRT2527 confirmed significant tumor growth inhibition in select MYC-amplified solid tumor PDX models. Taken together, this preclinical characterization supports the advancement of PRT2527 into clinical studies for transcriptionally addicted hematological malignancies and solid tumors with MYC amplification and/or dysregulation. Citation Format: Yang W. Zhang, Liang Lu, Min Wang, Dave Rominger, Stefan Ruepp, Kirsten Gallagher, William Gowen-MacDonald, Chaofeng Dai, Miles Cowart, Andrew Combs, Bruce Ruggeri, Peggy Scherle, Kris Vaddi. PRT2527 is a potent and selective CDK9 inhibitor that demonstrates anti-cancer activity in preclinical models of hematological malignancies and solid tumors with MYC amplification [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P237.

Abstract IAP0301: Bispecific T cell engagers (TCEs) for treatment of solid tumors: Challenges and opportunities

Abstract T cell-engaging bispecific antibody constructs (TCEs) have the potential to engage all cytotoxic T cells for redirected cancer cell lysis, including CD8, CD4, gamma/delta, NKT and regulatory T cells. TCEs transiently connect T cells with target cells leading to formation of a cytolytic synapse. Once activated by TCEs, T cells can adopt a serial lysis mode and increase troop size by their local proliferation. In numerous animal models, TCEs can eradicate large tumors as single-agent therapy. TCEs show a remarkable single-agent activity in hematological diseases, including ALL, NHL (DLBCL and FL) and AML. A CD19/CD3-bispecific TCE called blinatumomab (Blincyto) has been approved in 2014, and six other TCEs targeting CD20, BCMA and CD123 are in late-stage development. With complete response rates >50% and durability of responses, TCEs are in par with autologous CD19 CAR-T cells in NHL but are easier to manufacture and allow for a faster treatment start. Treatment of solid tumor indications with TCEs is not as successful as treatment of blood-borne cancers. This may be due to issues with tumor penetration, the hostile tumor microenvironment and the scarcity of T cells in cold tumors. A variety of TCEs explore their single-agent activity against solid tumors by targeting surface antigen like PSMA, GPC3, GD2, or HER-2. Enhancements in the form of combination therapy with checkpoint inhibitors, or 4-1BB and CD28 agonists are being explored as ways of augmenting solid tumor activity of TCEs. The first TCE showing robust anti-tumor activity in a solid tumor indication is targeting a gp100 peptide/MHC (developed by Immunocore). It is made from a soluble TCR fragment of very high affinity for the gp100 peptide HLA*0201 complex fused to an anti-CD3 scFv fragment. Although only few partial responses were observed in uveal melanoma patients, the single-agent treatment showed a very robust improvement in overall survival with a hazard ratio of 0.51 compared to investigators’ choice. This data will inspire the development of more TCEs that are specific for peptide/MHC complexes. This class of targets can also be addresses by TCR-mimetic antibodies. TCEs using such antibodies showed high anti-tumor activity in mouse models against MAGE-A4, p53 mutant or tyrosinase peptide/MHC complexes, all targets that are otherwise not amenable to classical TCEs. Another emerging opportunity for treating cancers are conditional TCEs. These are infused as inactive precursors. Inside tumors, the locally produced proteases convert the precursors into highly active TCEs. One example is the so called ProTriTACs, where a half-life extending albumin-binding domain masks the CD3-binding domain. The mask confers a 500-fold reduction in the cytolytic activity of the TCE. Inside tumors, the mask is cleaved off and a TCE is activated that has a very short serum half-life once it is released from the tumor. Conditional TCEs promise not only a wider therapeutic index but can also leverage as targets tumor-associated antigens that are widely expressed on tumors but also on healthy normal tissues, such as EGFR or EpCAM/TROP1. On-target toxicity of TCEs relates to the quality of target antigens. Finding more tumor-specific surface antigens, appropriate pMHC targets (e.g., mutant oncogene epitopes) and conditional T cell engagers are ways to address this challenge. Off-target toxicity of TCEs relates to T cell activation because of redirected target cell lysis. In the worst case, a cytokine release syndrome is induced. In the best case, a low-level cytokine release is contributing to the efficacy of TCEs. CRS can be managed by steroids, step dosing, anti-IL6 antibody and/or dasatinib. Another promising means is subcutaneous administration of TCEs. A dozen TCE programs currently explore this route, which allows reduction of Cmax and of the initial cytokine release. TCEs will soon become a major weapon in the arsenal of cancer therapy. They will not only work in blood-borne cancers but will soon conquer select solid tumor indications. Peptide/MHC-targeting and conditional TCEs are very promising approaches to achieve solid tumor activity of TCEs. Citation Format: Patrick A. Baeuerle. Bispecific T cell engagers (TCEs) for treatment of solid tumors: Challenges and opportunities [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr IAP0301.

Abstract 954: AO-176, a highly differentiated clinical stage anti-CD47 antibody, is efficacious in pre-clinical models of lymphoma

Abstract Overexpression of CD47 by tumor cells exploits an immune checkpoint that prevents tumor recognition and destruction by innate immune cells. Binding of tumor CD47 to SIRPα on macrophages and dendritic cells triggers a “don't eat me” signal that inhibits phagocytosis enabling escape from innate immune surveillance. Blockade of the CD47/SIRPα axis enables immune recognition and phagocytic clearance of tumor cells. We have developed a clinical stage CD47 targeting antibody AO-176, that is highly differentiated among agents in this class. AO-176 not only blocks the CD47/SIRPα interaction to induce tumor cell phagocytosis, but also: a) directly induces solid and hematologic tumor cell cytotoxicity and damage-associated molecular patterns (DAMPs); b) preferentially binds tumor versus normal cells, which is correlated with β1-integrin expression and localization; c) negligibly binds RBC; and d) exhibits improved binding at acidic pH as found in tumor microenvironments.Previously we have shown that AO-176 is efficacious in a variety of solid tumor xenograft models as well as in models of multiple myeloma and AML. Here, we show the therapeutic potential of AO-176 in pre-clinical models of lymphoma where CD47 is upregulated and associated with poor prognosis. Using a variety of cell based and in vivo models we show that AO-176 demonstrates increased binding to lymphoma cells at an acidic versus physiologic pH and that this binding and blocking of the do not eat me signal leads to enhanced phagocytosis of lymphoma cells either alone or in combination with rituximab. In addition, we show that AO-176 induces annexin V positivity in lymphoma cells as well as inducing a variety of DAMPs that ultimately may aid in inducing immunogenic cell death of the lymphoma cells. We also demonstrate that AO-176 is a potent tumor growth inhibitor in lymphoma xenograft models and appears to induce immune infiltrates as well as inflammatory cytokines.Taken together, these data show that AO-176 has strong therapeutic potential in lymphoma. AO-176 is currently being evaluated in clinical trials of select solid tumors (NCT03834948) and multiple myeloma (NCT04445701). Citation Format: Benjamin J. Capoccia, Michael J. Donio, John O. Richards, Ronald R. Hiebsch, Robyn J. Puro, Arun K. Kashyap, Daniel S. Pereira. AO-176, a highly differentiated clinical stage anti-CD47 antibody, is efficacious in pre-clinical models of lymphoma [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 954.

The next-generation pan-RAF inhibitor, KIN-2787, is active in class II and class III BRAF mutant models.

3116 Background: Oncogenic BRAF gene alterations, leading to aberrantly activated BRAF monomers (Class I mutations) or dimers (Class II and Class III mutations), are observed in approximately 6% of all human cancers. First-generation BRAF inhibitors targeting Class I BRAF mutants, including dabrafenib, encorafenib, and vemurafenib, provide significant clinical benefit to patients with BRAF V600 mutation-driven melanoma and select solid tumors as monotherapies or in combination with other targeted therapies. The currently approved BRAF inhibitors have not, however, proven to be effective in patients with Class II or III BRAF alterations which account for a large proportion (34%) of BRAF mutations. KIN-2787 is an orally available, potent and selective small molecule pan-RAF inhibitor specifically designed to inhibit Class II and III BRAF dimers, in addition to Class I mutants. Methods: The efficacy and tolerability of the pan-RAF inhibitor, KIN-2787, was evaluated in vitro and in vivo in Class I, II, and III BRAF mutation-driven human cancer models. Results: In biochemical assays, KIN-2787 showed low nanomolar to picomolar potency against RAF1, BRAF, and ARAF (IC50 0.06-3.46 nM) with minimal activity towards non-RAF kinases. In cell-based assays, KIN-2787 inhibited RAF activity, as measured by inhibition of downstream ERK phosphorylation (pERK), across multiple BRAF mutant cancer cell lines. Class II and III BRAF mutant cell lines were the most responsive when treated with KIN-2787 (IC50 < 50 nM); 19- and 7-fold more sensitive compared to cells harboring wild-type BRAF, respectively. Dose-dependent inhibition of A-375 (Class I), BxPC-3 (Class II), and WM3629 (Class III) BRAF mutant human xenograft tumor growth was attained with daily KIN-2787 treatment and was well-tolerated. A trend towards greater tumor responses was observed with twice daily (BID) compared to once daily (QD) dosing of KIN-2787; however, the two dosing regimens led to similar tumor growth inhibition (TGI) and regressions (mean TGI up to 101-118%; p ≤0.0001) at equivalent total daily doses. Furthermore, KIN-2787 led to a significant in vivo pharmacodynamic response using either regimen, however, prolonged target coverage, as measured by pERK, was achieved with BID dosing. The impact of KIN-2787 treatment on additional biomarkers, including transcriptional changes and MAPK pathway modulation in cell-based models and patient-derived samples, will be presented at the meeting. Conclusions: KIN-2787 is a next-generation pan-RAF inhibitor with pronounced in vitro and in vivo activity against human cancers driven by Class II and III BRAF mutations. A phase 1 dose escalation and expansion clinical trial evaluating the safety and efficacy of KIN-2787 monotherapy in patients with advanced or metastatic solid tumors harboring BRAF gene alterations, including Class II and III mutations, is expected to initiate in 2021.

A first-in-human study of AO-176, a highly differentiated anti-CD47 antibody, in patients with advanced solid tumors.

2516 Background: AO-176 is a humanized IgG2 antibody that specifically targets CD47. Expressed by multiple tumor types, CD47 binds to signal regulatory protein a (SIRPa) on phagocytes, including macrophages and dendritic cells. The CD47-SIRPa complex results in a “don’t eat me” signal that allows the tumor to escape removal by the innate immune system, disabling the generation of an adaptive immune response. The differentiated mechanisms of action of AO-176 include promotion of phagocytosis, direct tumor cell killing through programmed cell death type III and induction of damage associated molecular patterns/immunogenic cell death, preferentially binding to tumor cells vs. normal cells, and enhanced binding at an acidic pH as found in tumor microenvironments. AO-176 has negligible binding to RBCs. Methods: In a phase 1/2 first-in-human study (NCT03834948) of AO-176, pts with advanced solid tumors associated with high CD47 expression and an ECOG PS of 0-1 were enrolled into escalating dose cohorts of AO-176 given IV every 7 days. Objectives included evaluation of safety, dose-limiting toxicity (DLT) and recommended phase 2 dose (RP2D), antitumor activity, pharmacokinetic (PK) parameters and exploratory biomarkers. Results: As of 4 Jan 2021, 27 pts were enrolled (median age 64 years; 67% female; 67% ECOG PS 1; median [range] of 4 [1-7] prior therapies for metastatic disease). Dose levels of 1, 3, 10, 20 and 20 (using step-up dosing) mg/kg were evaluated in >250 infusions. Most common (>10%) treatment-related adverse events (TRAEs) of any grade were thrombocytopenia and infusion-related reaction (IRR) (33% each), anemia (22%) with no evidence of hemolysis, nausea (19%), and fatigue (15%). The only G3+ TRAE occurring in >10% of pts was asymptomatic, brief thrombocytopenia (22%). No platelet transfusions were given. DLTs included IRRs in 2 pts dosed at 20 mg/kg, and asymptomatic thrombocytopenia and a cerebrovascular accident in 1 pt each in the 20 mg/kg step-up cohort. The RP2D was 10 mg/kg. Implementation of additional pre-medication and a 6-hr infusion duration in cycle 1 eliminated subsequent IRRs. Dexamethasone tapering and shortening of the infusion duration to 2 hrs was successful in all pts after cycle 1. Interim PK analysis of AO-176 demonstrated consistent exposure with linear PK. The T1/2 was ̃5 days. One pt with endometrial carcinoma who had not responded to any of 4 prior systemic regimens had a confirmed PR and remains on study for >1 year. 7 pts had SD as a best response, with 2 pts (endometrial carcinoma, gastric cancer) on study for >6 mos. Conclusions: AO-176 is a well-tolerated, differentiated anti-CD47 therapeutic. Durable anti-tumor activity was observed. Evaluations of AO-176 in combination with paclitaxel in pts with select solid tumors (NCT03834948) and as a single-agent in pts with multiple myeloma (NCT04445701) are ongoing. Clinical trial information: NCT03834948.

A phase 1 study of SGN-B6A, an antibody-drug conjugate targeting integrin beta-6, in patients with advanced solid tumors (SGNB6A-001, Trial in Progress).

TPS3144 Background: The extracellular matrix (ECM) plays an important role in solid tumor pathogenesis and is a major focus of research and therapeutic targeting. Integrin beta-6 is a cell surface receptor that interacts with the ECM to mediate cellular adhesion. Integrin beta-6 is overexpressed in numerous solid tumors and its expression is a negative prognostic marker in cancers including colorectal, non-small cell lung, gastric, and cervical cancers. SGN-B6A is an investigational vedotin, an antibody-drug conjugate directed against integrin beta-6 to selectively deliver the cytotoxic agent monomethyl auristatin E, which binds tubulin and induces apoptosis. In multiple xenograft models, treatment with SGN-B6A resulted in tumor growth delay and regression in tumor volume when compared to non-binding control. Methods: SGNB6A-001 (NCT04389632) is a phase 1, first-in-human, open-label, multicenter study designed to evaluate the safety, tolerability, pharmacokinetics (PK), and antitumor activity of SGN-B6A in adults with select advanced solid tumors. Primary objectives are to evaluate the safety and tolerability of SGN-B6A in patients with advanced solid tumors, identify the maximum tolerated dose, and identify a recommended dose and schedule. The study has 2 parts: dose escalation (Part A) and dose expansion with multiple disease-specific cohorts and a biology cohort (Part B). SGN-B6A will initially be given by intravenous infusion on Days 1, 8, and 15 of 21-day cycles. The dose escalation (Part A) will be conducted using the modified toxicity probability interval method to determine a dose that demonstrates a dose-limiting toxicity rate of 25% with a 5% margin. The dose and schedule for Part B will be determined based on evaluation of safety, PK, and pharmacodynamic biomarkers. Response evaluations will be based on RECIST v1.1. Patients must be ≥18 years old and have histologically or cytologically confirmed metastatic or unresectable solid malignancy within one of the following tumor types: non-small cell lung cancer, head and neck squamous cell cancer, breast cancer, esophageal cancer, ovarian cancer, cutaneous squamous cell cancer, exocrine pancreatic adenocarcinoma, bladder cancer, cervical cancer, or gastric cancer. After an appropriate dose and schedule are determined in Part A, safety and preliminary antitumor efficacy of SGN-B6A will be evaluated in indication-specific cohorts (Part B). This study is ongoing in sites across North America and Europe. Clinical trial information: NCT04389632.

Phase 2 trial of cabozantinib in children and young adults with refractory sarcomas, Wilms tumor, and rare tumors: Children's Oncology Group Study (ADVL1622).

10010 Background: Cabozantinib is an inhibitor of multiple receptor tyrosine kinases (RTKs) including MET, VEGFR2, RET, and AXL. Preclinical and clinical data support these RTKs as potential therapeutic targets; Safety, tolerability, and responses were demonstrated in a COG phase 1 trial. We conducted a multi-center open label phase 2 trial to determine the activity of cabozantinib in select pediatric solid tumors (NCT02867592). Methods: Patients age 2-30 years old with selected relapsed or refractory cancer that was measurable (RECISTv.1.1) were eligible. Using a Simon minimax design, patients were enrolled to six strata: Osteosarcoma (OS), Ewing sarcoma (EWS), rhabdomyosarcoma (RMS), non-rhabdomyosarcoma soft tissue sarcoma (NRSTS), Wilms tumor (WT), and rare tumor (a non-statistical stratum including tumors of specific histologies or molecular features). Cabozantinib (40 mg/m2/day) was administered on a continuous schedule (1 cycle = 28 days). For the OS stratum, activity was determined based on objective response rate (ORR, complete response (CR) + Partial response (PR)) or disease control success defined as at least stable disease (SD) for ≥ 4 months. For all other strata, the primary endpoint was ORR. Pharmacokinetics were performed in patients < 19 years. Results: Between May 2017- Oct 2020, 109 patients enrolled (105 eligible, 104 evaluable for response and toxicity). Median age was 15.8 (range 5.6-27.1) years; 55 were male. In the OS stratum, 10/29 (34%) patients had central review confirmed disease control ≥ 4 months (2 PR, 8 SD), exceeding the protocol-defined criteria for activity of cabozantinib in OS. Median duration of therapy was 3 cycles (range 1-28+). In EWS, RMS, NRSTS, and WT strata (n = 13 evaluable patients each) no PR or CR were observed. In the rare tumor stratum (n = 23), 1/4 patients with renal cell carcinoma, 1/1 patients with RET fusion positive papillary thyroid cancer had a PR, and 1 patient with medullary thyroid cancer had a delayed PR. SD ≥ 6 cycles was seen in patients with EWS (n = 2), NRSTS (n = 5), WT (n = 3), and hepatocellular carcinoma (n = 1). At data cutoff (12/31/2020), 430 treatment cycles were administered; two patients remain on therapy. Cycle 1 and later cycle dose limiting toxicities (DLT) were seen in 20 (19%) and 39 (38%) patients, respectively. Common DLT were elevated liver enzymes, bilirubin, and lipase, hyponatremia, weight loss, anorexia, nausea, vomiting, wound dehiscence, palmar-plantar erythrodysesthesia, and pneumothorax. Day 1 pharmacokinetics (mean ± SD, n = 16) demonstrated a maximum plasma concentration of 556 ± 376 ng/ml, half-life 106 ± 102 hours, and area under the curve (AUC0-24h) 8093 ± 4368 ng•h/mL. Conclusions: Cabozantinib is active in patients with relapsed refractory OS and deserves further study in this disease. PRs were also seen in select carcinomas. Activity is limited in other sarcomas and WT. Clinical trial information: NCT02867592.

Testing of B7-H3 targeting antibody-drug conjugate (ADC) MGC018 in models of pediatric solid tumors by the Pediatric Preclinical Testing Consortium (PPTC).

10037 Background: B7-H3 (encoded by the CD276 gene) is an immunoregulatory molecule that is widely expressed in pediatric embryonal tumors and sarcomas, while expression is limited for normal tissues. Among PPTC models, osteosarcoma models showed highest CD276 transcript levels followed by Wilms tumor, neuroblastoma, rhabdomyosarcoma, and Ewing sarcoma. Protein expression by IHC generally followed expression at the RNA level, with high expression by IHC observed across a range of models. MGC018 is a duocarmycin-based humanized ADC targeting B7-H3 that shows selective cytotoxicity for B7-H3 expressing cancer cells, robust in vivo activity against a range of adult cancer preclinical models, a favorable pharmacokinetic and safety profile in cynomolgus monkeys, and has entered clinical testing for adults with cancer. Herein we report the in vivo antitumor activity of MGC018 against preclinical models of pediatric solid tumors. Methods: MGC018 was tested at 6 mg/kg administered intraperitoneally (IP) on Day 1. SYD988, an anti-CD20 ADC with the same linker and payload as MGC018, was used as a control arm at 6 mg/kg IP on Day 1. Osteosarcoma models, due to their slower growth kinetics and lower rates of tumor regression, were tested with n = 10 mice per arm, while the sarcoma and neuroblastoma models were tested with n of 1 or n of 2 designs, respectively. Activity was evaluated using response criteria mirroring clinical criteria (progressive disease (PD), stable disease (SD), partial response (PR), complete response (CR), and maintained CR (MCR)], by minimum relative tumor volume across all models, and by event-free survival (EFS) comparisons between treatment groups. Results: For neuroblastoma models (n = 9), 3 and 2 neuroblastoma models showed objective responses (PR/CR/MCR) or SD, respectively, to MGC018, while none showed an objective response or SD to SYD988. For osteosarcoma, results are mature for 1 of 5 models, with this model showing an MCR response to MGC018 and a PD response to SYD988. For Ewing sarcoma (n = 5), a PR and MCR were observed to MGC018 with the remaining models showing PD; for SYD988 a single CR was observed with the remaining 4 models showing PD. For rhabdomyosarcoma (n = 3) 2 MCR and 1 PD were noted for MGC018, while only PD was noted for SYD988. EFS duration exceeding 100 days to a single dose of MGC018 was observed for 2 rhabdomyosarcoma, 1 Ewing sarcoma, and 1 neuroblastoma model. Evaluation of the relationship between B7-H3 expression and response to MGC018 will be performed when results from all studies are completed. Conclusions: B7-H3 is an important target for immuno-oncology agents for childhood cancers. Our results provide proof-of-principle for the ability of MGC018 to produce profound antitumor activity in select pediatric solid tumor models in a B7-H3 specific manner.

Lenvatinib plus pembrolizumab for patients with previously treated biliary tract cancers in the multicohort phase 2 LEAP-005 study.

4080 Background: Second-line treatment options for patients with biliary tract cancers (BTC) are limited. Lenvatinib, an anti-angiogenic multikinase inhibitor, in combination with the programmed death-1 immune checkpoint inhibitor pembrolizumab, has demonstrated promising antitumor activity with a manageable safety profile in patients with select advanced solid tumors. LEAP-005 (NCT03797326) is evaluating the efficacy and safety of lenvatinib plus pembrolizumab in patients with previously treated advanced solid tumors; here we present results from the BTC cohort of LEAP-005. Methods: In this nonrandomized, open-label, phase 2 study, eligible patients were aged ≥18 years with histologically or cytologically documented advanced (metastatic and/or unresectable) BTC with disease progression after 1 prior line of therapy, measurable disease per RECIST v1.1, ECOG PS of 0‒1, and tissue sample evaluable for PD-L1 expression. Patients received lenvatinib 20 mg once daily plus pembrolizumab 200 mg Q3W for up to 35 cycles (approximately 2 years) or until confirmed disease progression, unacceptable toxicity, or withdrawal of consent. Treatment with lenvatinib could continue beyond 2 years in patients experiencing clinical benefit. Primary endpoints were ORR (per RECIST v1.1 by blinded independent central review) and safety. Secondary endpoints were the disease control rate (DCR; comprising CR, PR, and SD), duration of response (DOR), PFS, and OS. Tumor imaging was performed Q9W from treatment initiation for 54 weeks, then Q12W to week 102, and Q24W thereafter. Results: 31 patients were enrolled in the BTC cohort (ECOG PS 1, 55%; 84% ex-US). As of April 10, 2020, median time from first dose to data cutoff (DCO) was 9.5 months (range, 3.1‒11.9), with 8 patients on treatment at DCO. There were 3 (10%) PRs and 18 (58%) SDs. ORR was 10% (95% CI, 2‒26), and DCR was 68% (95% CI, 49‒83). Median DOR was 5.3 months (range, 2.1+ to 6.2). Median PFS was 6.1 months (95% CI, 2.1‒6.4). Median OS was 8.6 months (95% CI, 5.6 to NR). Treatment-related AEs occurred in 30 patients (97%), including 15 (48%) who had grade 3 AEs; there were no grade 4 or 5 treatment-related AEs. 2 (6%) discontinued treatment due to treatment-related AEs (myocarditis, pyrexia; n = 1 each). The most frequent treatment-related AEs were hypertension (42%), dysphonia (39%), diarrhea (32%), fatigue (32%), and nausea (32%). 14 patients (45%) had immune-mediated AEs and 1 patient (3%) had an infusion-related reaction. Conclusions: Lenvatinib plus pembrolizumab demonstrated encouraging efficacy and manageable toxicity in patients with advanced BTC who had received 1 line of prior therapy. Based on these data, enrollment in the BTC cohort has been expanded to 100 patients. Clinical trial information: NCT03797326.

Novel Approach Using Administrative Claims to Evaluate Trends in Oncology Multigene Panel Testing for Patients Enrolled in Medicare Advantage Health Plans.

PURPOSETo develop an approach to identify and evaluate recent use of multigene panel testing over time.METHODSWe conducted a retrospective database analysis using medical and pharmacy claims data. Medicare Advantage Prescription Drug Plan members diagnosed with select malignant solid tumors were identified. The pattern of somatic genetic testing for each patient was evaluated from January 2016 through December 2018. Tests were classified by the number of genes tested in the panel: < 50 (small or medium) and ≥ 50 (large).RESULTSAn initial feasibility study using our novel approach for identifying panel tests resulted in 2.4 and 1.2 times more large and medium panels, respectively, identified compared with using procedure codes alone. A total of 121,675 eligible patients were identified, with 131,915 unique cancer cases. Overall, 5,457 (4.5%) patients received any panel test from 2016 to 2018. We found the number of tests performed each quarter increased from 238 in Q1 of 2016 to 755 in Q4 of 2018. The highest number of cases were genitourinary cancers; however, the highest proportion of cancer-related genetic testing was among patients with respiratory cancer. Across all tumor types, the proportion of large-panel tests performed as a function of all multigene panel tests increased from 20.7% of tests in Q1 of 2016 to 46.4% of tests in Q4 of 2018. The three cancer categories with the highest count of cancer-related panel tests, respiratory cancer, GI cancer, and female reproductive cancer, had a consistently greater proportion receiving a panel test at any point postindex.CONCLUSIONAcross a variety of cancers, use of somatic, large-panel cancer-related genetic testing, as a proportion of all somatic cancer-related genetic testing, increased from 2016 to 2018, although testing overall was low.

Tumor-infiltrating CD8+ T cells can be resident, but exhaustion markers rather than CD69 correlate with residence and tumor specificity

Abstract Tumor infiltrating lymphocytes (TILs) represent a heterogeneous population of both pathogen-specific bystander and tumor-specific CD8+ T cells. Within select solid tumors, the expression of exhaustion markers PD-1 and CD39 has been used to discriminate between pathogen-specific and tumor-specific cells. Independent studies across numerous types of solid tumors have also shown that CD8+ TILs can exhibit distinct signatures that imply residence, however, the migrational properties of TILs have not been fully elucidated. In this study, we employed parabiosis migration assays in a mouse model of breast cancer and demonstrated that both virus-specific bystander and tumor-specific CD8+ T cells within the tumor microenvironment (TME) can be resident. Canonical markers of resident-memory T cells (TRM), including CD69, failed to discriminate between resident cells and recent migrants. However, the expression of markers associated with T cell dysfunction (PD-1, CD39, Tim-3, Lag-3) identified a population of tumor-specific cells and was tightly correlated with residence within the TME. Thus, TRM exist within tumors, durable intratumoral residence was not well informed by common markers associated with TRM in healthy tissues, and the expression of exhaustion markers correlated with both tumor specificity and durable residence.

Lenvatinib plus pembrolizumab for patients with previously treated biliary tract cancers in the multicohort phase II LEAP-005 study.

321 Background: Second-line treatment options for patients with biliary tract cancers (BTC) are limited. Lenvatinib, an anti-angiogenic multikinase inhibitor, in combination with the programmed death-1 immune checkpoint inhibitor pembrolizumab, has demonstrated promising antitumor activity with a manageable safety profile in patients with select advanced solid tumors. LEAP-005 (NCT03797326) is evaluating the efficacy and safety of lenvatinib plus pembrolizumab in patients with previously treated advanced solid tumors; here we present results from the BTC cohort of LEAP-005. Methods: In this nonrandomized, open-label, phase II study, eligible patients were aged ≥18 years with histologically or cytologically documented advanced (metastatic and/or unresectable) BTC with disease progression after 1 prior line of therapy, measurable disease per RECIST v1.1, ECOG PS of 0‒1, and tissue sample evaluable for PD-L1 expression. Patients received lenvatinib 20 mg once daily plus pembrolizumab 200 mg Q3W for up to 35 cycles (approximately 2 years) or until confirmed disease progression, unacceptable toxicity, or withdrawal of consent. Treatment with lenvatinib could continue beyond 2 years in patients experiencing clinical benefit. Primary endpoints were ORR (per RECIST v1.1 by blinded independent central review) and safety. Secondary endpoints were the disease control rate (DCR; comprising CR, PR, and SD), duration of response (DOR), PFS, and OS. Tumor imaging was performed Q9W from treatment initiation for 54 weeks, then Q12W to week 102, and Q24W thereafter. Results: 31 patients were enrolled in the BTC cohort (ECOG PS 1, 55%; 84% ex-US). As of April 10, 2020, median time from first dose to data cutoff (DCO) was 9.5 months (range, 3.1‒11.9), with 16 patients on treatment at DCO. There were 3 (10%) PRs and 18 (58%) SDs. ORR was 10% (95% CI, 2‒26), and DCR was 68% (95% CI, 49‒83). Median DOR was 5.3 months (range, 2.1+ to 6.2). Median PFS was 6.1 months (95% CI, 2.1‒6.4). Median OS was 8.6 months (95% CI, 5.6 to NR). Treatment-related AEs occurred in 30 patients (97%), including 15 (48%) who had grade 3‒4 AEs; there were no treatment-related deaths. 2 (6%) discontinued treatment due to treatment-related AEs (myocarditis, pyrexia; n = 1 each). The most frequent treatment-related AEs were hypertension (42%), dysphonia (39%), diarrhea (32%), fatigue (32%), and nausea (32%). 14 patients (45%) had immune-mediated AEs and 1 patient (3%) had an infusion-related reaction. Conclusions: Lenvatinib plus pembrolizumab demonstrated encouraging efficacy and manageable toxicity in patients with advanced BTC who had received 1 line of prior therapy. Based on these data, enrollment in the BTC cohort has been expanded to 100 patients. Clinical trial information: NCT03797326.