Antitumor Activity In Preclinical Models Research Articles

10P DS-6000a, a novel CDH6-targeting antibody-drug conjugate with a novel DNA topoisomerase I inhibitor DXd, demonstrates potent antitumor activity in preclinical models

Human Cadherin 6 (CDH6) is a single transmembrane protein consisting of 790 amino acids classified into the type 2 cadherin family. Human CDH6 is specifically expressed in the brain and kidneys during the development phase and has been reported to systemically decrease CDH6 expression in the adult body. CDH6 expression is increased specifically in renal cell carcinoma (RCC) and ovarian cancer (OVC). Therefore, CDH6 could be an attractive target for cancer therapy. We created DS-6000a, a CDH6-targeting antibody-drug conjugate (ADC) using an enzymatically cleavable tetrapeptide-based linker, and a high drug-to-antibody ratio (DAR 7 to 8) with a novel DNA topoisomerase I inhibitor (DXd).

13P SY-5609, a highly potent and selective oral CDK7 inhibitor, exhibits robust antitumor activity in preclinical models of KRAS mutant cancers as a single agent and in combination with chemotherapy

Mutational KRAS activation drives oncogenic processes including aberrant cell cycle progression. CDK7 inhibition has been shown to target two fundamental processes in cancer: transcription and cell cycle control. SY-5609 is a CDK7 inhibitor in development in patients with solid tumors including pancreatic and lung cancers (NCT04247126). Here we report on SY-5609 preclinical activity in models of KRAS-mutant pancreatic ductal adenocarcinoma (PDAC) and non-small-cell lung cancer (NSCLC).

Cytolytic Activity of CAR T Cells and Maintenance of Their CD4+ Subset Is Critical for Optimal Antitumor Activity in Preclinical Solid Tumor Models.

Simple SummaryAdoptively transferred T cells expressing recombinant chimeric antigen receptors (CAR T cells) have been approved for the therapy of hematological malignancies of the B cell lineage. However, CAR T cell therapy for patients with solid tumors so far has shown limited benefits. Correlative clinical studies of patients with hematological malignancies have suggested that less differentiated CAR T cells have improved anti-leukemic activity. We have therefore investigated the role of differentiation on the anti-tumor activity of CAR T cells targeting the solid tumor antigen HER2 in preclinical models. We utilized different activation/expansion protocols, and explored whether different co-stimulatory domains in the CAR construct influence the short- and long-term efficacy of HER2-CAR T cells. We demonstrate that the CAR T cell product with the highest proportion of effector cells and maintaining a good balance of CD4+/CD8+ cells is the most effective against solid tumors both in vitro and in vivo.Correlative clinical studies of hematological malignancies have implicated that less differentiated, CD8+-dominant CAR T cell products have greater antitumor activity. Here, we have investigated whether the differentiation status of CAR T cell products affects their antitumor activity in preclinical models of solid tumors. We explored if different activation/expansion protocols, as well as different co-stimulatory domains in the CAR construct, influence the short- and long-term efficacy of CAR T cells against HER2-positive tumors. We generated T cell products that range from the most differentiated (CD28.z; OKT3-antiCD28/RPMI expansion) to the least differentiated (41BB.z; OKT3-RetroNectin/LymphoONE expansion), as judged by cell surface expression of the differentiation markers CCR7 and CD45RA. While the effect of differentiation status was variable with regard to antigen-specific cytokine production, the most differentiated CD28.z CAR T cell products, which were enriched in effector memory T cells, had the greatest target-specific cytolytic activity in vitro. These products also had a greater proliferative capacity and maintained CD4+ T cells upon repeated stimulation in vitro. In vivo, differentiated CD28.z CAR T cells also had the greatest antitumor activity, resulting in complete response. Our results highlight that it is critical to optimize CAR T cell production and that optimal product characteristics might depend on the targeted antigen and/or cancer.

Selective Inhibition of the Second Bromodomain of BET Family Proteins Results in Robust Antitumor Activity in Preclinical Models of Acute Myeloid Leukemia.

Dual bromodomain BET inhibitors that bind with similar affinities to the first and second bromodomains across BRD2, BRD3, BRD4, and BRDT have displayed modest activity as monotherapy in clinical trials. Thrombocytopenia, closely followed by symptoms characteristic of gastrointestinal toxicity, have presented as dose-limiting adverse events that may have prevented escalation to higher dose levels required for more robust efficacy. ABBV-744 is a highly selective inhibitor for the second bromodomain of the four BET family proteins. In contrast to the broad antiproliferative activities observed with dual bromodomain BET inhibitors, ABBV-744 displayed significant antiproliferative activities largely although not exclusively in cancer cell lines derived from acute myeloid leukemia and androgen receptor positive prostate cancer. Studies in acute myeloid leukemia xenograft models demonstrated antitumor efficacy for ABBV-744 that was comparable with the pan-BET inhibitor ABBV-075 but with an improved therapeutic index. Enhanced antitumor efficacy was also observed with the combination of ABBV-744 and the BCL-2 inhibitor, venetoclax compared with monotherapies of either agent alone. These results collectively support the clinical evaluation of ABBV-744 in AML (Clinical Trials.gov identifier: NCT03360006).

Abstract 1260: First-in-class, orally bioavailable KRASG12V(ON) tri-complex inhibitors, as single agents and in combinations, drive profound anti-tumor activity in preclinical models of KRASG12V mutant cancers

Abstract KRASG12V mutant cancers represent a significant unmet medical need with nearly 44,000 new diagnoses annually in the US. The KRASG12V mutation occurs frequently in multiple tumor histotypes; the incidence in NSCLC, CRC and pancreatic cancers is 6%, 10% and 26%, respectively. RAS proteins are small GTPases that drive cell proliferation and survival when bound to GTP. Mutant RAS proteins exist predominantly in the GTP-bound (RAS(ON)) state, leading to excessive downstream signaling via interaction with effectors such as RAF. The intrinsic GTP hydrolysis rate of KRASG12V is significantly lower than that of either KRASG12C or KRASG12D. Therefore, targeting the KRASG12V(ON) state will be critical for maximal suppression of this oncogenic driver. No targeted, direct inhibitors of KRASG12V(ON) have been described to date. We have built a pipeline of small molecule inhibitors targeting multiple oncogenic RAS(ON) mutants. Here we describe the preclinical profile of KRASG12V(ON) inhibitors that promote a tri-complex between the inhibitor, the immunophilin cyclophilin A (CypA), and the active GTP-bound state of KRASG12V. In cancer cell lines bearing KRASG12V mutations, KRASG12V(ON) inhibitors trigger an immediate disruption of RAS-effector interactions, leading to attenuation of RAS pathway signaling, potent (sub-nM EC50) growth suppression, and apoptosis. KRASG12V(ON) inhibitors produce deep, durable, and dose-dependent suppression of tumor RAS pathway activation in vivo following oral administration. An extended duration of tumor pharmacodynamic activity, relative to plasma exposure, is observed that likely reflects retention of the inhibitors in tumor tissue due to high affinity binding to CypA. In human tumor xenograft models of KRASG12V mutant NSCLC, CRC and pancreatic cancers, oral administration of KRASG12V(ON) inhibitors is well-tolerated and drives profound and durable tumor regressions, with complete responses in some animals. KRASG12V(ON) inhibitors also downregulate immune checkpoint proteins PD-L1 and CD73 on KRASG12V mutant cancer cells, changes which can support enhanced anti-tumor immunity. The ability to target the GTP-bound form of mutant KRASG12V permits a broad array of combination opportunities in cancer types where single agent KRASG12V(ON) inhibition may be insufficient, for example with agents targeting pathway nodes both upstream (e.g. SHP2, SOS1) and downstream (e.g. MEK, ERK) of RAS, as well as parallel pathways (e.g. mTORC1). Tri-complex inhibitors that target KRASG12V(ON) are predicted to combat escape mechanisms in RAS-addicted cancer cells characterized by an increased pool of activated KRASG12V(ON). These inhibitors may lead to an attractive, targeted therapeutic option for the treatment of RAS-addicted cancers with a very high unmet medical need. Citation Format: Elena Koltun, Jim Cregg, Meghan A. Rice, Dan M. Whalen, Rebecca Freilich, Jingjing Jiang, Richard Hansen, Alun Bermingham, John E. Knox, Jay Dinglasan, Kyle Seamon, Cristina Blaj, Stephanie S. Chang, Yang Liu, Jun Huang, Kang-Jye Chou, Laura McDowell, Bianca J. Lee, David Wildes, Zhengping Wang, Mallika Singh, Adrian L. Gill, Jacqueline A. Smith. First-in-class, orally bioavailable KRASG12V(ON) tri-complex inhibitors, as single agents and in combinations, drive profound anti-tumor activity in preclinical models of KRASG12V mutant cancers [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 1260.

Abstract 981: BCL-2 inhibitor APG-2575 and homoharringtonine (HHT) synergistically induces apoptosis and inhibits tumor growth in preclinical models of acute myeloid leukemia and myelodysplastic syndromes (AML/MDS)

Abstract The AML treatment landscape has improved dramatically in the past decade, with improved objective response rates and overall survival after treatment with newly approved targeted therapies. BCL-2 inhibition combined with a hypomethylating agent or low-dose cytosine arabinoside (Ara-C) is also effective in previously untreated elderly patients who are not candidates for standard induction therapy. However, the effect of BCL-2 inhibition is commonly weakened when tumor cells upregulate antiapoptotic protein MCL-1 to escape apoptosis. Thus, combination therapy is introduced to suppress MCL-1 levels. HHT (omacetaxine mepesuccinate) has been widely used in Chinese patients with AML for 30 years. As an inhibitor of protein synthesis, HHT decreases MCL-1. This study investigated the effect of combining clinical stage BCL-2 selective inhibitor APG-2575 with HHT in AML and MDS cells, as well as murine xenograft tumor models. In AML (MV-4-11, OCI-AML-3) and MDS (SKM-1) cell lines, single-agent HHT exerted stronger antiproliferative and apoptogenic activities compared to APG-2575 (as assessed by Cell Titer Glo assay or flow cytometry). When combined, these treatments synergistically inhibited cellular proliferation and induced apoptosis. In a mouse xenograft tumor model derived from MV-4-11 cells, APG-2575 demonstrated limited antitumor activity, with a T/C (Treated/Control tumor volume %) value of 63% whereas HHT showed stronger activity, with T/C equal to 30%. Most importantly, these antitumor effects were potentiated when APG-2575 and HHT were combined, yielding a T/C value of 3% and partial regression in all treated tumors. Mechanistically, BCL-2 inhibition with APG-2575 decreased BCL-2:BIM complexes and but increased MCL-1:BIM complexes, as liberated BIM was re-sequestered by MCL-1. On the other hand, concomitant treatment with HHT abolished induction of MCL-1:BIM complexes. Besides BIM complexes, MCL-1:PUMA and MCL-1:BAK pairings also decreased after exposure to HHT. The decrease in MCL-1 complex coincided with its downregulation at protein levels. Thus, under such an MCL-1-supressed condition facilitated by HHT treatment, the freed proapoptotic proteins (BIM, PUMA, BAK) more potently manifested apoptotic signals triggered by APG-2575. In summary, APG-2575 synergizes with HHT to potentiate antitumor activity in preclinical models of AML/MDS. HHT suppresses MCL-1 protein, preventing or abolishing formation of MCL-1:BIM, MCL-1:PUMA, and MCL-1:BAK complexes, and hence allowing prodeath proteins to fully engage in tumor cell apoptosis induction. Our results provide scientific rationale for clinical development of APG-2575 plus HHT in patients with AML/MDS. Citation Format: Douglas D. Fang, Qiuqiong Tang, Yanhui Kong, Tao Rong, Qixin Wang, Jing Deng, Dajun Yang, Yifan Zhai. BCL-2 inhibitor APG-2575 and homoharringtonine (HHT) synergistically induces apoptosis and inhibits tumor growth in preclinical models of acute myeloid leukemia and myelodysplastic syndromes (AML/MDS) [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 981.

Abstract 2077: Activity of DHODH inhibitor BAY2402234 in subcutaneous and intracranial models of SCLC

Abstract Introduction: BAY2402234 is a potent and specific orally administered inhibitor of dihydroorotate dehydrogenase (DHODH) which showed anti-tumor activity in preclinical models of AML and is under clinical evaluation in myeloid malignancies (NCT03404726). Small cell lung cancer (SCLC) is a highly metastatic malignancy (the brain being a frequent metastatic site), which carries a dismal clinical prognosis. Previous preclinical research indicated that SCLC was particularly sensitive to DHODH inhibition, and in the current investigation the activity of BAY2402234 in this tumor indication was evaluated. Experimental Procedures: A variety of in vivo models derived from human SCLC samples were evaluated: (1) cell-line derived xenograft (CDX) subcutaneous models; (2) a CDX intracranial model; and (3) patient-derived xenograft (PDX) subcutaneous models. As is typical for SCLC, most of these models harbored mutations in both p53 and Rb1. BAY2402234 was administered orally either once daily or on an intermittent schedule (4 days on/3 days off). Standard-of-care (SoC) therapies were included in some experiments. Tumor tissue and plasma were collected for pharmacodynamic analyses. Results: In subcutaneous CDX models, BAY2402234 exhibited robust anti-tumor activity, including tumor regressions in some models. Strong anti-tumor activity was also observed in various subcutaneous PDX models, including activity in a model resistant to SoC therapy. In an intracranial tumor model, BAY2402234 significantly enhanced survival compared to the vehicle-treated cohort. Both dosing schedules tested were well-tolerated and highly active. Pharmacodynamic analyses to quantify the level of target inhibition observed in the various models are ongoing. Conclusions: The results of this investigation confirm and extend previous preclinical results and indicate that BAY2402234 may represent a novel treatment for SCLC, including patients with brain metastases. RESTRICTED Citation Format: Stefan Kaulfuss, Andreas Janzer, Gerhard Siemeister, Renan Borowicz, Katrin Jaensch, Katrin Gutberlet, Ricarda Schlenz, Andrea Triller, Ashley Eheim, Michael Jeffers, Sven Christian. Activity of DHODH inhibitor BAY2402234 in subcutaneous and intracranial models of SCLC [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 2077.

Abstract LB118: Mechanisms underlying synergistic activity in MYD88MTDLBCL of KT-413, a targeted degrader of IRAK4 and IMiD substrate

Abstract Relapsed/refractory DLBCL remains an incurable disease, and single-agent therapies typically show low response rates and/or transient clinical responses. Oncogenic MYD88 mutations occur in ~25% of DLBCL and drive constitutive NFkB activation, promoting proliferation and survival. Despite its role in tumor biology, targeting MYD88MT by inhibiting or degrading IRAK4 alone, a key component of the MYD88 complex, does not drive significant antitumor activity in preclinical models. One potential reason is the frequent redundant NFkB pathway activation by co-mutations, highlighting the need for combination therapies to effectively target the NFkB pathway in DLBCL. To address this challenge, we have developed IRAKIMiDs, heterobifunctional degraders that simultaneously degrade both IRAK4 and IMiD substrates, as a rational therapeutic combination in a single molecule. IRAKIMiDs show increased antitumor activity in vitro and in vivo in MYD88MT cells as compared to IMiD or IRAK4-targeting alone, highlighting suggesting their potential as single agents in R/R DLBCL.Our lead IRAKIMiD, KT-413, is a potent degrader of IRAK4 (DC50 6nM) and IMiD substrates (Ikaros/Aiolos DC50 2nM), inducing rapid and potent cell killing in vitro and complete and sustained tumor regressions in vivo in MYD88MT models of DLBCL. This activity is superior to the IMiD CC-220, which has similar activity against IMiD substrates (Ikaros/Aiolos DC50 1 nM), supporting the synergistic role of IRAK4 degradation in the context of IMiD biology. We show here that the combined activity of these 2 mechanisms drives a synergistic effect on NFkB and IRF4 signaling with greater downstream effect on NFkB and type 1 interferon (IFN) signaling and cell cycle gene expression than either mechanism alone. In THP1 cells engineered with NFkB and IRF4 reporters, KT-413 but not CC-220 inhibits TLR-stimulated NFkB and IRF4 transcription, supporting a role for IRAK4 but not IMiDs in MYD88-driven survival and proliferation signals. IMiDs have previously been shown to modulate type1 IFN signaling through downregulation of IRF4. We propose that simultaneous targeting of both NFkB and type 1 IFN signaling with KT-413 drives synergistic cell killing in MYD88MT cells. In MYD88MT OCI-Ly10 cells, KT-413 leads to greater IRF4 downregulation, increased type 1 IFN signaling, and preferential downregulation of NFkB pathway and cell cycle transcripts when compared to CC-220. These data support the hypothesis that the synergistic activity of targeting IRAK4 and IMiD substrates by KT-413 in MYD88MT DLBCL is a result of dual targeting of NFkB and IRF4/Type1 IFN through degradation of both IRAK4 and IMiD substrates,driving significantly greater cell killing as compared to either mechanism alone, supporting the potential for the first single agent targeted therapy in MYD88MT DLBCL. KT-413 is on track for initiation of a Phase 1 trial in B cell lymphoma in 2H 2021. Citation Format: Christine R. Klaus, Scott F. Rusin, Kirti Sharma, Samyabrata Bhaduri, Matthew M. Weiss, Alice A. McDonald, Michele F. Mayo, Duncan Walker, Rahul Karnik. Mechanisms underlying synergistic activity in MYD88MTDLBCL of KT-413, a targeted degrader of IRAK4 and IMiD substrate [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 LB118.

Abstract CT029: Pediatric phase 2 trial of the WEE1 inhibitor adavosertib (AZD1775) and irinotecan: A Children's Oncology Group Study (ADVL1312)

Abstract Background: Inhibition of the WEE1 kinase by adavosertib (AZD1775) potentiates replicative stress from genomic instability or chemotherapy, and demonstrated anti-tumor activity in preclinical models of pediatric cancer. This study reports the phase 2 expansion of the ADVL1312 phase I/II trial combining irinotecan and adavosertib in children and adolescents with relapsed/refractory solid and CNS tumors. Methods: Patients (< 21 yrs old) with measurable or MIBG-evaluable relapsed/refractory neuroblastoma (Part B), medulloblastoma/CNS embryonal tumors (Part C) or rhabdomyosarcoma (Part D) were treated with irinotecan (90 mg/m2/dose) and adavosertib (85 mg/m2/dose) orally for 5-days every 21-days. Any patient who received at least one dose was considered evaluable for response. Using a Simon's two stage design the combination was considered effective if there were three out of twenty responses in parts B and D or six out of nineteen responses in part C. Tumor tissue was analyzed for ATRX deficiency by multiplex immunofluorescence of ultrabright telomere foci and ATRX, and where available, prior tumor genomic analyses. Results: Twenty eligible patients with neuroblastoma, with a median age of nine years old (6-19) were included in Part B. They had a median of three prior chemotherapy regimens (1-7); nineteen patients (95%) had prior irinotecan and seventeen (85%) received prior radiation therapy. The combination therapy resulted in three objective responses confirmed by central review (estimated response rate of 16.7%) meeting the protocol defined efficacy endpoint for Part B. The responses included a measurable partial response (11 cycles), MIBG evaluable complete response (9 cycles) and MIBG and marrow evaluable partial response (18 cycles). In addition, there were three patients with prolonged stable disease of 8, 11 and 13 cycles. Two of the three patients with objective responses had tumors with predicted ATRX deficiency, while the third did not have available archival tumor. Of the nine neuroblastoma patient tumors with predicted ATRX deficiency, 4 (44%) had objective responses or prolonged stable disease. In part C, of 9 patients eligible for response, 1 patient with pineoblastoma had a confirmed partial response (9 cycles) and another with medulloblastoma had prolonged stable disease (11 cycles). In part D, of 10 eligible patients, 2 had stable disease of 8 and 10 cycles. Part C and D did not meet the protocol defined efficacy endpoint. The combination was well tolerated with one patient experiencing a dose limiting toxicity that resolved with dose reduction. Conclusion: This the first phase 2 clinical trial of adavosertib in pediatrics and the first in combination with irinotecan. The combination was of sufficient activity to support further study in neuroblastoma, and possibly other pediatric tumor types with recurrent ATRX mutation. Citation Format: Kristina A. Cole, Heba Ijaz, Lea Surrey, Mariarita Santi-vicini, Xiaowei Liu, Charles G. Minard, John M. Maris, Stephan Voss, Elizabeth Fox, Brenda Weigal. Pediatric phase 2 trial of the WEE1 inhibitor adavosertib (AZD1775) and irinotecan: A Children's Oncology Group Study (ADVL1312) [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 CT029.

Abstract 1530: Anti-HER2 CAR monocytes demonstrate targeted anti-tumor activity and enable a single day cell manufacturing process

Abstract Recent advances in cell therapy have led to significant efficacy in hematologic malignancies, but solid tumors remain an intractable challenge. We have previously developed a CAR macrophage (CAR-M) adoptive cell therapy platform and demonstrated potent anti-tumor activity in pre-clinical models. CAR-M overcome several of the barriers to efficacy in the solid tumor setting - trafficking, immunosuppression, lymphocyte exclusion, and antigen heterogeneity. Currently, CAR-M are generated via ex vivo differentiation of peripheral blood monocytes into macrophages prior to genetic manipulation. In order to streamline the manufacturing process, improve cell yields, and potentially improve tumor infiltration, we sought to evaluate the feasibility of directly engineering CD14+ monocytes to express CAR. Using the chimeric adenoviral vector Ad5f35, we engineered primary human CAR-monocytes to target tumors overexpressing HER2. CAR expression and viability both exceeded 90%. Anti-HER2 CAR-monocytes produced pro-inflammatory cytokines in response to antigen, specifically phagocytosed HER2 overexpressing target cells, and eradicated HER2-overexpressing tumor cells in a time and dose-dependent manner. CAR-monocytes efficiently differentiated into CAR-expressing macrophages in response to various maturation factors and cytokines within 3-5 days. Adenoviral based gene modification resulted in the upregulation of several pro-inflammatory markers on CAR-monocytes and pre-conditioned these cells to differentiate into M1 macrophages in the absence of exogenous M1 polarization factors. The M1 phenotype was maintained when CAR-monocytes were challenged with immunosuppressive cytokines in vitro. These cells demonstrated potent effector function after differentiation into macrophages, regardless of exposure to GM-CSF, M-CSF, or immunosuppressive factors. Anti-HER2 CAR monocytes carried broadly expressed myeloid chemokine receptors and responded to a panel of chemotactic factors. In order to optimize the cell manufacturing process associated with CAR-M, we established a closed-system, ultra-rapid CAR monocyte process. This process enabled same day manufacturing of the final CAR monocyte cell product, significantly reducing the cost of goods associated with autologous cell therapy as well as “vein to vein” time. This study demonstrated the successful development of CAR-monocytes with direct anti-tumor activity and capacity to differentiate into M1 polarized CAR-M. In addition, we established an ultra-rapid same-day CAR monocyte manufacturing process. The CAR-monocyte platform represents an advance in the field of adoptive cell therapy. Citation Format: Linara Gabitova, Brett Menchel, Rashid Gabbasov, Stefano Pierini, Andrew Best, Kayleigh Ross, Yumi Ohtani, Daniel Blumenthal, Sascha Abramson, Thomas Condamine, Michael Klichinsky. Anti-HER2 CAR monocytes demonstrate targeted anti-tumor activity and enable a single day cell manufacturing process [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 1530.

Abstract 2786: A FcgR IIB tumor enriching anti-CD137 novel antibody to avoid liver Immuno-toxicity

Abstract CD137 (4-1BB/TNFRSF9) is a costimulatory T-cell receptor belonging to the TNF receptor superfamily which is transiently expressed on T cell and NK cells. Targeting CD137 or its natural ligand 4-1BB ligand (4-1BBL) has important implications in many clinical conditions, including cancer. Anti-CD137 agonistic anti-CD137 antibodies have shown potent, often curative anti-tumor activity in preclinical models. In depth analysis revealed that 4-1BB-mediated anti-cancer effects are based on its ability to induce activation of cytotoxic T lymphocytes and high amounts of cytokines, including IFN-γ. However, this approach has suffered significant setback in the clinic due to either dose-dependent severe liver toxicity (e.g. Urelumab), or lack of single agent activity in the case of Utomilumab. Multiple therapeutics that attempt to restrict 4-1BB agonism to the tumor microenvironment and minimize systemic exposure have emerged. Here we present a novel antibody targeting 4-1BB receptor, named HLX25 with engineered Fc region to enhance the binding to FcγR IIB. In vitro, HLX25 induces comparable or superior CD137 activation and IL-2 release compared to Urelumab and Utomilumab, suggesting potentially a better safety profile. We showed that HLX25 binds to unique non-ligand competing epitope, which is different from both Urelumab and Utomilumab. In vivo, HLX25 shows potent dose-dependent single agent anti-tumor activity as low as 0.3mg/kg in MC38 model without sign of liver toxicity up to 20 mg/kg, suggesting superior efficacy and better safety profile. Citation Format: Jie Xue, Jen-Kuan Chang, Chen Dong, Yi-Ting Mao, Pallavi Raghavendra, Ou Li, Hassan Issafras, Wenfeng Xu, Weidong Jiang. A FcgR IIB tumor enriching anti-CD137 novel antibody to avoid liver Immuno-toxicity [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 2786.

Sy-1365, a Potent and Selective CDK7 Inhibitor, Exhibits Anti-Tumor Activity in Preclinical Models of Hematologic Malignancies, and Demonstrates Interactions with the BCL-XL/BCL2 Mitochondrial Apoptosis Signaling Pathway in Leukemia

Introduction: The transcriptional kinase CDK7 has been implicated in the pathogenesis of multiple malignancies, including hematologic malignancies, and may play important roles in regulation of oncogenic transcriptional dependencies and in regulation of the mitochondrial apoptosis machinery in tumors. SY-1365, a selective inhibitor of CDK7, was developed to exploit tumor dependencies driven by CDK7 and is in clinical development in patients with advanced solid tumors. We have previously reported that SY-1365 selectively induces apoptosis in leukemic cells relative to non-malignant cells in vitro, and demonstrates anti-tumor activity in AML xenografts. Here we report that SY-1365 has potent inhibitory activity against a broad panel of hematologic malignancies in vitro and ex vivo, induces regressions in AML xenografts using a clinically relevant dosing regimen, and demonstrates synergy with the BCL2 inhibitor venetoclax in AML cells in vitro.Methods: SY-1365 dose-response curves were measured using the ATP-lite assay in a panel of 85 leukemia and lymphoma cell lines in vitro, and in a panel of 226 patient-derived tumor samples from 5 leukemic indications cultured ex vivo. In vivo tumor inhibitory activity was evaluated using once weekly (QW) and twice weekly (BIW) dosing regimens in ML-2 and Kasumi-1 AML xenografts. Growth-rate (GR) adjusted dose response curves were used to classify cell lines into low and high sensitivity groups, and were evaluated relative to RNA expression data to identify markers predictive of sensitivity to SY-1365. Synergy between SY-1365 and venetoclax was evaluated in vitro using KG-1 AML cells.Results: In 42 leukemia lines, SY-1365 had a median IC50 of 11nM (range 1-79nM), with 48% (20/42) demonstrating particularly low IC50s (<10nM). In 43 lymphoma lines, the median IC50 was 6nM (range 1-39nM), with 59% (27/46) demonstrating low IC50s (<10nM). Similarly, SY-1365 demonstrated potent inhibitory activity against patient-derived leukemia samples cultured ex vivo (median IC50 of 28nM), with 82% (185/226) of the samples showing IC50 below 100nM and 8% (19/226) under 10nM. Furthermore, analysis of growth rate (GR) in hematologic tumor cell lines showed that <10nM SY-1365 induced cytotoxicity (GR<0) in 19% (8/42) of leukemia and 21% (9/43) of lymphoma lines. To evaluate SY-1365 anti-tumor activity in vivo, 2 AML cell lines that demonstrate cytotoxic responses to SY-1365 in vitro (Kasumi-1 and ML-2) were grown as subcutaneous xenografts in mice. QW and BIW dosing of 40mg/kg SY-1365 induced tumor regressions in Kasumi-1 xenografts, and BIW dosing induced tumor stasis in ML-2 xenografts. Tumor growth inhibition was detected with a 20mg/kg BIW dosing regimen in both models. Comparison of SY-1365 sensitivity with RNA expression in hematologic tumor cell lines revealed that lower expression of BCL2L1, which encodes the mitochondrial apoptosis inhibitor BCL-XL, was highly predictive of sensitivity in leukemia cell lines (Accuracy=89%, FDR<0.05); no such relationship was observed in lymphoma lines. Considering the established role of BCL2 and the mitochondrial apoptosis pathway in leukemia, we reasoned that BCL-XL low-expressing leukemias, in addition to being sensitive to SY-1365, would also be reliant on BCL2 for survival. Indeed, in vitro combination studies demonstrated synergistic inhibitory activity of SY-1365 with the BCL2 inhibitor venetoclax in KG-1 AML cells. A potential synergistic interaction with SY-1365 and venetoclax is currently being explored in vivo with AML xenografts.Conclusions: SY-1365 shows potent in vitro inhibitory activity in multiple hematological indications and can induce AML xenograft tumor regression in mice. In vitro exploratory biomarker and tumor cell inhibitory combination studies in AML suggest a role for mitochondrial apoptosis signaling in mediating sensitivity to SY-1365 and support the evaluation of a combination with venetoclax. SY-1365 is currently being assessed in a phase 1 trial in adult patients with advanced solid tumors (NCT03134638). The results described here support the potential for additional exploration in patients with hematological malignancies. DisclosuresHodgson:Syros Pharmaceuticals: Employment, Equity Ownership. Johannessen:Syros Pharmaceuticals: Employment, Equity Ownership. Rajagopal:Syros Pharmaceuticals: Employment, Equity Ownership. Hu:Syros Pharmaceuticals: Employment, Equity Ownership. Orlando:Syros Pharmaceuticals: Employment, Equity Ownership. Eaton:Syros Pharmaceuticals: Employment, Equity Ownership. McKeown:Syros Pharmaceuticals: Employment. Tyner:Takeda Pharmaceutical Company: Research Funding; Agios Pharmaceuticals: Research Funding; Incyte Corporation: Research Funding; Gilead: Research Funding; Janssen Pharmaceutica: Research Funding; Syros: Research Funding; Aptose Biosciences: Research Funding; Seattle Genetics: Research Funding; Constellation Pharmaceuticals: Research Funding; Genentech: Research Funding; Array Biopharma: Research Funding; AstraZeneca: Research Funding; Leap Oncology: Consultancy. Sprott:Syros Pharmaceuticals: Employment, Equity Ownership. Fritz:Syros Pharmaceuticals: Employment, Equity Ownership. Di Tomaso:Syros Pharmaceuticals: Employment.

Edo-S101, a Bendamustine (BDM)/ Histone-Deacetylase Inhibitor (HDACi) Fusion Molecule, Demonstrates Potent Preclinical Activity Against T-Cell Malignancies and Overcomes BDM-Resistance

Introduction: T-cell and natural killer (NK)-cell lymphomas encompass a heterogeneous spectrum of malignancies with variable degrees of biological and clinical aggressiveness and different patterns of nodal/extra nodal dissemination. Despite advances in understanding of their genetic landscape, treatment options for these tumors are limited and survival remains dismal especially in patients (pts.) who relapse/progress after frontline treatment. Therefore, development of new active agents is a pressing medical need in this setting. The unconventional alkylator BDM and HDACi are clinically effective in pts. with recurring disease and the combination of these agents was suggested as a way to overcome early resistance and improve response and survival rates in T-cell tumors. Since EDO-S101 is a fusion molecule that combines the active structures of BDM and the pan-HDACi vorinostat to simultaneously damage DNA and block damage repair, we investigated its antitumor activity in preclinical models of human T- and NK- lymphomas.Methods: We assessed the patterns of EDO-S101 cytotoxicity and its regulatory effects on genes involved in DNA-damage/repair, apoptosis and drug resistance on a large panel of cell lines representative of most T-lymphoma subtypes, including precursor T-cell lymphoma/leukemia (pTCL; MOLT-4, KE-37, Jurkat, CCRF-CEM), anaplastic large T-cell lymphoma (ALCL; SR-786, SUDHL1) and cutaneous T-cell lymphoma (CTCL; HUT78, MYLA, HH, PB2B, MAC-2A). As a further model, we exploited an ALCL cell line (SUDHL1-R100) selected for resistance to BDM. SUDHL1-R100 display a growth pattern indistinguishable from parental cells in the presence of BDM (100 μmol/L).Results: EDO-S101 induced a significant time- and dose-dependent inhibition of growth and survival in all T-cell lines, with a IC50 at 48 hrs (0.33 to 0.68 μmol/L), that was at least 90% and 50% lower than IC50 of BDM (10.5 to 23.67 μmol/L) and vorinostat (0.42 to 1.17 μmol/L) in the same cell lines. No significant differences emerged across various cell lines as to sensitivity to EDO-S101. Notably, growth inhibitory effects of EDO-S101 were 35% to 40% higher than those achieved by the concomitant exposure of tumor cells to BDM and vorinostat at equimolar concentrations. A significant induction of the DNA double strand breaks marker pγH2AX, along with decreased levels of Thr-1989 pATR and Polo-like kinase 1 (PLK1) were consistently observed in pTCL, ALCL and CTCL cell lines, indicating that EDO-S101 triggered inappropriate mitotic entry with unrepaired DNA damage. In addition, qRT-PCR results showed upregulation of the proapototic genes NOXA, p21 and/or p27 in pTCL, CTCL and ALCL cells. Among DNA repair genes, EDO-S101-induced downregulation of ATM, ATR and EXO1 was paralleled by an increase of MGMT transcripts. Most intriguingly, BDM-resistant ALCL cells (SUDHL1-R100) were highly sensitive to EDO-S101, with an IC50 of only 0.72 μmol/L, but less responsive to vorinostat (IC50: 2.17 μmol/L) than parental cells (IC50: 1.46 μmol/L). Exposure to EDO-S101 also resulted in transcriptional regulation of components of the PI3K pathway, mainly the PI3Kα and δ isoforms and mTOR. These findings, prompted experiments showing that EDO-S101 at sublethal concentrations was highly synergic with the predominant PI3Kα/δ inhibitor copanlisib in inducing cell death of tumor T- and NK-cells. Finally, exposure to EDO-S101 (1.0 μmol/L) for 48 hrs resulted in a sustained upregulation of surface PD1 and PD-L1 in most tumor T- and NK-cell lines, as a possible result of its HDACi component.Conclusions: We have shown for the first time that the BDM/vorinostat fusion molecule EDO-S101 is very active in preclinical models of T/NK cell lymphomas. It shows a superior activity towards different types of tumor T- and NK-cells than its single components administered either individually or in combination by also overcoming acquired resistance to BDM. Data indicate that EDO-S101 simultaneously damages DNA and interferes on its repair pathways in tumor T-cells. We also showed synergy between EDO-S101 and PI3Kα/δ inhibitors possibly due to regulatory effects on specific components of the PI3K pathway as well as a potential for this agent to enhance PD1-blockade strategies. A clinical trial is ongoing to evaluate efficacy and safety of EDO-S101 in pts. with relapsed/refractory hemopoietic malignancies including T-cell lymphomas. DisclosuresMehrling:Mundipharma-EDO Gmbh, Basel, CH: Employment. Pinto:Celgene: Honoraria; Merck Sharp Dome: Honoraria; Millenium Takeda: Research Funding; Roche: Honoraria; Bristol Myers Squibb: Honoraria; Gilead: Honoraria; Helssin: Honoraria; Mundipharma EDO: Speakers Bureau.

Abbv-621 Is a Novel and Potent TRAIL Receptor Agonist Fusion Protein That Induces Apoptosis Alone and in Combination with Navitoclax and Venetoclax in Hematological Tumors

Cell death can be initiated through activation of the extrinsic and intrinsic apoptotic signaling pathways. Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), a member of the TNF superfamily of cytokines, preferentially triggers the extrinsic apoptotic pathway by binding as a trimer to two closely related cell surface death receptors, TRAIL-R1 (DR4) and TRAIL-R2 (DR5). When these receptors undergo trimerization, it leads to the formation of the death-inducing signaling complex (DISC) to recruit and activate downstream caspases that ultimately leads to apoptotic cell death. Since TRAIL was found to induce apoptosis, several TRAIL receptor agonists have been developed for the treatment of cancer. ABBV-621 is a novel, second generation TRAIL receptor agonist that is currently being tested in Phase 1 clinical trials. It is an engineered fusion protein consisting as an IgG1-Fc linked to a single chain trimer of TRAIL subunits resulting in a total of six death receptor binding sites per molecule in order to maximize receptor clustering. ABBV-621 exhibited potent single agent activity in acute myeloid lymphoma (AML) and diffuse large B-cell lymphoma (DLBCL) cell lines following 24hrs treatment. This activity was rapid and mechanism-based since activation of downstream apoptotic signaling events (caspase activation, mitochondrial depolarization, phosphatidylserine exposure) were observed as early as 1 hour following the addition of ABBV-621, and cell death could be completely blocked with the pan caspase inhibitor z-VAD-FMK . In vivo, ABBV-621 demonstrated robust single agent anti-tumor activity in pre-clinical models of AML and DLBCL.The intrinsic apoptotic pathway is regulated by the BCL-2 protein family which controls the release of cytochrome c from the mitochondria resulting in the activation of downstream caspases. Because the two apoptotic pathways are linked, the intrinsic pathway can influence cell death mediated through the extrinsic pathway. The elevated expression of the anti-apoptotic proteins, BCL-2 and BCL-XL, can inhibit the activation of the intrinsic apoptotic pathway and enable resistance to anti-cancer therapeutics, including TRAIL. Venetoclax (ABT-199), a BCL-2 selective inhibitor, and navitoclax (ABT-263) a BCL-2/BCL-XL selective inhibitor, were tested in combination with ABBV-621 in a number of hematologic tumor cell lines in vitro and in vivo . The anti-tumor activity of ABBV-621 in combination with venetoclax or navitoclax exceeded that of either agent tested alone in pre-clinical and AML and DLBCL xenograft models.Collectively, these data highlight that targeting the extrinsic apoptosis signaling pathway with either ABBV-621 alone or in combination with venetoclax/navitoclax to harness the intrinsic apoptosis signaling pathway has potential therapeutic benefit in hematologic malignancies.Disclosures:All authors are employees of AbbVie. The design, study conduct, and financial support for this research were provided by AbbVie. AbbVie participated in the interpretation of data, review, and approval of the publication. DisclosuresTahir:Abbvie: Employment, Equity Ownership. Smith:Abbvie: Employment, Equity Ownership. Solomon:Abbvie: Employment, Equity Ownership. Zhang:Abbvie: Employment, Equity Ownership. Xue:Abbvie: Employment, Equity Ownership. Xiao:Abbvie: Employment, Equity Ownership. Cheng:Abbvie: Employment, Equity Ownership. Buchanan:Abbvie: Employment, Equity Ownership. Morgan-Lappe:Abbvie: Employment, Equity Ownership. Phillips:Abbvie: Employment, Equity Ownership.

Preclinical Evaluation of MEDI2228, a BCMA-Targeting Pyrrolobenzodiazepine-Linked Antibody Drug Conjugate for the Treatment of Multiple Myeloma

Despite remarkable progress in treatment over the past two decades, multiple myeloma (MM) remains an incurable disease. B-cell maturation antigen (BCMA, TNFRSF17) is a suitable therapeutic target for the treatment of MM due to its restricted expression on normal plasma cells and universal expression in myeloma cells. Targeting BCMA with an antibody-drug conjugate (ADC) is an attractive therapeutic option, combining the specificity of a monoclonal antibody with a potent cytotoxic drug to preferentially eliminate antigen-positive cells for the treatment of cancer.Here we describe MEDI2228, a novel ADC that targets BCMA. MEDI2228 is composed of a fully human antibody site-specifically conjugated to a DNA cross-linking pyrrolobenzodiazepine (PBD) dimer via a protease-cleavable linker. Flow cytometry studies show that MEDI2228 is rapidly internalized and trafficked to lysosomes. Upon release, the warhead binds to the minor-groove and cross-links DNA, leading to DNA damage and apoptotic cell death.The anti-tumor activity of MEDI2228 was assessed in vitro in 10 MM and plasma cell leukemia (PCL) cell lines encompassing several cytogenetic subtypes. MEDI2228 was highly active in 8 of 10 MM cell lines tested (IC50 range 6 to 210 ng/mL) including cell lines with high (~19,000 receptors/cell) or low (~930 receptors/cell) expression of BCMA. In addition, MEDI2228 is active in the presence of bone marrow stromal cells, which have been shown to play a role in chemotherapy resistance, and in cell models resistant to Lenalidomide. In vivo antitumor activity was evaluated in 4 separate MM and PCL subcutaneous xenograft models and 2 PCL disseminated xenograft models, where a single injection of MEDI2228 induced tumor regression at doses as low as 0.1 mg/kg.A soluble form of BCMA (sBCMA) has been detected in the serum of MM patients (Sanchez et. al. Br J Haematol 2012) and is comprised of the entire extracellular domain of the molecule (Laurent et. al. Nat Commun 2015). Therefore, sBCMA could diminish the effects of antibody-based therapies. We found that levels of sBCMA are elevated in the sera of MM patients compared with healthy donor controls, with levels ranging from 23 ng/mL to 728 ng/mL. The functional features of sBCMA and recombinant monomeric human BCMA are similar (Laurent et. al. Nat Commun 2015). Therefore, to mitigate the potential effects of sBCMA on the efficacy of our drug, the antibody component of MEDI2228 was selected because it possessed weak binding to recombinant monomeric human BCMA and strong binding to membrane-bound BCMA. The in vitro cytotoxicity of MEDI2228 in the presence of clinically-relevant levels of sBCMA was evaluated using NCI-H929 and MM.1S cells. MEDI2228 was cytotoxic to both MM.1S and NCI-H929 in vitro, killing an average of 95% of tumor cells in the presence of sBCMA at levels up to 720 ng/mL with little impact on IC50. ADCs developed from antibodies that possessed a similar affinity between monomeric BCMA and membrane-bound BCMA exhibited a sBCMA-dose dependent drop in potency, with a 20-fold shift in IC50 in the presence of 720 ng/mL sBCMA.MM is a clonally heterogeneous disease, and previously it has been reported that a small population of CD19+CD138- clonogenic cells can be identified in the bone marrow (BM) of MM patients (Matsui et. al. Blood 2004). We used flow cytometric sorting of CD19 and CD138 populations and outgrowth in methocult to confirm that CD19+CD138- cells are the clonogenic cells in MM BM samples. Furthermore, we found that this population contains the same light chain restriction, genetic translocation, and aberrant phenotype as the MM plasma cells. These cells express BCMA and can be killed by MEDI2228 in methocult outgrowth assays.These data demonstrate that MEDI2228 exhibits potent antitumor activity in preclinical models of MM. Importantly, in vitro experiments suggest that this activity is maintained in the presence of sBCMA. MEDI2228, bearing a potent PBD payload, may effectively target both the bulk myeloma plasma cells as well as the more quiescent, CD19+CD138- clonogenic cells, which may offer an opportunity for more durable clinical response in this genetically heterogeneous disease. DisclosuresKinneer:MedImmune: Employment. Meekin:MedImmune: Employment. Varkey:MedImmune: Employment. Xiao:MedImmune: Employment; Bristol-Myers Squibb: Employment. Zhong:MedImmune: Employment. Breen:MedImmune: Employment. Hurt:MedImmune: Employment. Thomas:MedImmune: Employment. Flynn:MedImmune: Employment. Hynes:MedImmune: Employment. Bezabeh:Salubris Biotherapeutics Inc: Employment; MedImmune: Employment. Chen:MedImmune: Employment. Wetzel:MedImmune: Employment. Chen:MedImmune: Employment. Anderson:Gilead Sciences: Membership on an entity's Board of Directors or advisory committees; MedImmune: Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Oncopep: Other: scientific founder; C4 Therapeutics: Other: scientific founder; Millenium Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees. Herbst:MedImmune: Employment. Tice:MedImmune: Employment.

Therapeutic Targeting of Interferon Regulatory Factor 4 with Next Generation Antisense Oligonucleotides Produces Robust In Vivo Antitumor Activity in Preclinical Models of Multiple Myeloma

Despite significant recent advances in therapeutic options, multiple myeloma (MM) remains an incurable disease, and novel agents targeting novel molecular pathways with activity in advanced patients are urgently needed. Interferon Regulatory Factor 4 (IRF4) is a transcription factor involved in immune responses in normal B and T cells, and is strongly implicated in the development of hematological malignancies, especially MM. Although recent publications have pointed to IRF4 as a driver oncogene in the progression of MM, it is considered an intractable target by conventional therapeutic approaches.Here we describe an antisense oligonucleotide (ASO) approach to selectively target IRF4. Administration of next generation human IRF4 ASOs via ‘free-uptake’ (without transfection) to a large panel of human MM cell lines resulted in a dose-dependent IRF4 reduction with concomitant induction of apoptosis. ASO-mediated IRF4 depletion also decreased the levels of c-Myc, another key oncogene in MM. MM cells were sensitive to even modest depletion of IRF4 (<50%), suggesting the strong dependence of MM cells on IRF4 for their survival. IRF4 ASOs also enhanced the sensitivity of the tumor cells to the treatment of IMiD (lenalidomide), proteasome inhibitor (Bortezomib) and BTK inhibitor (Ibrutinib) in MM cell, including KMS-11, JJN3 and MM1.R. In addition, Bortezomib-resistant clones of KMS-11 cells established from a long-term exposure to the drug remained sensitive to IRF4 inhibition. Importantly, in two different subcutaneously implanted MM tumor models, systemic administration of 2 independent human IRF4 ASOs depleted IRF4 protein levels in tumors and inhibited the growth of tumors compared to control treatment. Moreover, in a clinically relevant MM mouse model where human MM cells accumulate in the mouse bone marrow, treatment with human IRF4 ASOs substantially prolonged the survival of the tumor-bearing animals along with specific downregulation of human IRF4 and its downstream gene c-Myc. Finally, systematic treatment of mice with mouse-selective IRF4 ASOs at 50 mg/kg, twice a week for 4 weeks was well tolerated in normal mice, which is consistent with the lack of phenotypes observed in IRF4 heterozygous animals. Taken together, these results suggest that MM cells rely heavily on the survival pathway mediated by IRF4 and that selective knockdown of IRF4 by next generation ASOs is an attractive therapeutic strategy for the treatment of patients with advanced treatment-refractory MM. DisclosuresZhou:Ionis Pharmaceuticals: Employment, Equity Ownership. Schmidt:Ionis Pharmaceuticals: Employment. Kim:Ionis Pharmaceuticals: Employment. MacLeod:Ionis Pharmaceuticals: Employment.

Fibroblast growth factor receptor (FGFR) inhibitor rogaratinib in patients with advanced pretreated squamous-cell non-small cell lung cancer over-expressing FGFR mRNA: The SAKK 19/18 phase II study.

e21119 Background: A substantial proportion of patients with squamous lung cell carcinoma (SQCLC) (46%) exhibit tumor overexpression of fibroblast growth factor receptor (FGFR) messenger ribonucleic acid (mRNA). Rogaratinib is a novel pan-FGFR inhibitor with anti-tumor activity in pre-clinical models as a single agent in FGFR pathway-addicted tumor models. Phase I data showed promising activity and good safety profile. The objective of the SAKK 19-18 trial was to determine clinical activity and safety of rogaratinib in patients with advanced SQCLC overexpressing tumor FGFR1-3 mRNA. Methods: Patients with metastatic SQCLC, previously treated with systemic treatment, overexpressing tumour FGFR mRNA were treated with rogaratinib 600 mg BID until progression of disease or drug intolerance. A rate ≤15% of PFS at 6 months was considered uninteresting, whereas a PFS rate at 6 months ≥38% was considered promising. Ten patients were needed in the first stage with at least 2 achieving 6 months PFS in order to continue the accrual. Results: Between May and November 2020, 49 patients were screened and 20 were classified FGFR positive. Among them15 patients were registered in the trial and the first 10 were assessed for the first stage analysis. Most commons treatment related adverse events (TRAEs) were hyperphosphatemia (60%), diarrhoea (20%), and dry mouth (20%). Grade ≥3 TRAEs occurred in 50% of the patents with Hypercalcemia being the most frequent one (20%). Among 10 first patients only 1 achieved 6 months PFS while 2 was the boundary required for continuing this trial. Conclusions: Despite preliminary signal of activity, rogaratinib failed to improve PFS in patients overexpressing tumor FGFR mRNA. Further studies on a more reliable biomarker are needed, the development of rogaratinib in SQCLC has been put on hold by Bayer and the SAKK 19/18 study was terminated early due to lack of efficacy. Clinical trial information: NCT03762122.

LEAP-005: A phase 2 multicohort study of lenvatinib plus pembrolizumab in patients with previously treated selected solid tumors—Results from the colorectal cancer cohort.

3564 Background: Pembrolizumab (pembro), an anti-PD-1 antibody, is approved for the treatment of patients (pts) with unresectable or metastatic microsatellite instability-high (MSI-H) or mismatch repair (MMR) deficient colorectal cancer, both as first-line treatment and after progression following treatment with fluoropyrimidine, oxaliplatin, and irinotecan. The combination of lenvatinib, a multiple receptor tyrosine kinase inhibitor, and anti-PD-1 treatment showed synergistic antitumor activity in preclinical models. LEAP-005 (NCT03797326) is evaluating the efficacy and safety of lenvatinib plus pembro in pts with previously treated advanced solid tumors. We present findings from the colorectal cancer cohort. Methods: In this nonrandomized, open-label, phase 2 study, adult pts (aged ≥18 y) with histologically/cytologically documented metastatic and/or unresectable colorectal cancer, non–MSI-H/pMMR tumor per local determination, previous treatment with oxaliplatin and irinotecan in separate lines of therapy, measurable disease per RECIST v1.1, ECOG PS of 0‒1, and a tissue sample evaluable for PD-L1 expression were eligible. Pts received lenvatinib 20 mg QD plus pembro 200 mg Q3W for up to 35 cycles of pembro (̃2 y) or until confirmed disease progression, unacceptable toxicity, or withdrawal of consent. Treatment with lenvatinib could continue beyond 2 y in pts with clinical benefit. Primary endpoints were ORR (per RECIST v1.1 by blinded independent central review) and safety. Secondary endpoints included disease control rate (DCR), duration of response (DOR), PFS, and OS. Tumor imaging was performed Q9W from treatment initiation for 54 wks, then Q12W to week 102, and Q24W thereafter. Results: 32 pts with colorectal cancer received treatment with lenvatinib plus pembro (median age, 56 y [range, 36-77]; male, 81%; 3L, 91%); median time from first dose to data cutoff (April 10, 2020) was 10.6 mo (range, 5.9-13.1). ORR was 22% (95% CI, 9–40; table). Grade 3–5 treatment-related AEs occurred in 16 (50%) pts. Treatment-related AEs led to treatment discontinuation in 3 pts (grade 2 ischemic stroke [n = 1], grade 3 increased liver transaminases [n = 1], grade 5 intestinal perforation [n = 1]). Conclusions: In pts with previously treated advanced non–MSI-H/pMMR colorectal cancer, lenvatinib plus pembro demonstrated promising antitumor activity and a manageable safety profile. Enrollment in the colorectal cohort was expanded to 100 pts. Clinical trial information: NCT03797326. [Table: see text]

IL-13Rα2 gene expression is a biomarker of adverse outcome in patients with adrenocortical carcinoma.

Adrenocortical carcinoma (ACC) is a rare but aggressive endocrine malignancy that usually results in a fatal outcome. To allow the better clinical management and reduce mortality, we searched for clinical and molecular markers that are reliable predictor of disease severity and clinical outcome in ACC patients. We determined a correlation between the overexpression of IL-13Rα2 and the clinical outcome in ACC patients using comprehensive data available in The Cancer Genome Atlas (TCGA) database. The dataset of 79 ACC subjects were divided into groups of low, medium, or high expression of IL-13Rα2 as determined by RNA-seq. These patients were also stratified by length of survival, overall survival, incidence of a new tumor event, incidence of metastasis, and production of excess hormones. We report a correlation between IL-13Rα2 expression and survival of subjects with ACC. High expression of IL-13Rα2 in ACC tumors was significantly associated with a lower patient survival rate and period of survival compared to low expression (p = 0.0084). In addition, high IL-13Rα2 expression was significantly associated with a higher incidence of new tumor events and excess hormone production compared to low or medium IL-13Rα2 expression. Within the cohort of patients that produced excess hormone, elevated IL-13Rα2 expression was significantly associated with a lower survival rate. Additionally, IL-13Rα1 had a potential relationship between transcript level and ACC survival. Our results and promising antitumor activity in preclinical models and trials indicate that IL-13Rα2 expression is an important prognostic biomarker of ACC disease outcome and a promising target for therapeutic treatment of ACC.

The PSMA-targeting Half-life Extended BiTE Therapy AMG 160 has Potent Antitumor Activity in Preclinical Models of Metastatic Castration-resistant Prostate Cancer.

Metastatic castration-resistant prostate cancer (mCRPC) remains a disease with high unmet medical need, as most patients do not achieve durable response with available treatments. Prostate-specific membrane antigen (PSMA) is a compelling target for mCRPC. It is highly expressed by primary and metastatic prostate cancer cells, with increased expression after progression on androgen deprivation therapy. We developed AMG 160, a half-life extended, bispecific T-cell engager immuno-oncology therapy that binds PSMA on prostate cancer cells and cluster of differentiation 3 on T cells for treatment of mCRPC. AMG 160 was evaluated in vitro and in mCRPC xenograft models. AMG 160 tolerability was assessed in nonhuman primates (NHP). AMG 160 activity as monotherapy and in combination with a PSMA-imaging agent, novel hormonal therapy, and immune checkpoint blockade was evaluated. AMG 160 induces potent, specific killing of PSMA-expressing prostate cancer cell lines in vitro, with half-maximal lysis of 6-42 pmol/L. In vivo, AMG 160 administered weekly at 0.2 mg/kg engages T cells administered systemically and promotes regression of established 22Rv-1 mCRPC xenograft tumors. AMG 160 is compatible with the imaging agent gallium 68-labeled PSMA-11, and shows enhanced cytotoxic activity when combined with enzalutamide or an anti-programmed death-1 antibody. AMG 160 exhibits an extended half-life and has an acceptable safety profile in NHPs. The preclinical characterization of AMG 160 highlights its potent antitumor activity in vitro and in vivo, and its potential for use with known diagnostic or therapeutic agents in mCRPC. These data support the ongoing clinical evaluation of AMG 160 in patients with mCRPC.See related commentary by Kamat et al., p. 2675.