Antitumor Activity In Preclinical Models Research Articles

Lisaftoclax (APG-2575) Is a Novel BCL-2 Inhibitor with Robust Antitumor Activity in Preclinical Models of Hematologic Malignancy.

Development of B-cell lymphoma 2 (BCL-2)-specific inhibitors poses unique challenges in drug design because of BCL-2 homology domain 3 (BH3) shared homology between BCL-2 family members and the shallow surface of their protein-protein interactions. We report herein discovery and extensive preclinical investigation of lisaftoclax (APG-2575). Computational modeling was used to design "lead" compounds. Biochemical binding, mitochondrial BH3 profiling, and cell-based viability or apoptosis assays were used to determine the selectivity and potency of BCL-2 inhibitor lisaftoclax. The antitumor effects of lisaftoclax were also evaluated in several xenograft models. Lisaftoclax selectively binds BCL-2 (Ki < 0.1 nmol/L), disrupts BCL-2:BIM complexes, and compromises mitochondrial outer membrane potential, culminating in BAX/BAK-dependent, caspase-mediated apoptosis. Lisaftoclax exerted strong antitumor activity in hematologic cancer cell lines and tumor cells from patients with chronic lymphocytic leukemia, multiple myeloma, or Waldenström macroglobulinemia. After lisaftoclax treatment, prodeath proteins BCL-2‒like protein 11 (BIM) and Noxa increased, and BIM translocated from cytosol to mitochondria. Consistent with these apoptotic activities, lisaftoclax entered malignant cells rapidly, reached plateau in 2 hours, and significantly downregulated mitochondrial respiratory function and ATP production. Furthermore, lisaftoclax inhibited tumor growth in xenograft models, correlating with caspase activation, poly (ADP-ribose) polymerase 1 cleavage, and pharmacokinetics of the compound. Lisaftoclax combined with rituximab or bendamustine/rituximab enhanced antitumor activity in vivo. These findings demonstrate that lisaftoclax is a novel, orally bioavailable BH3 mimetic BCL-2-selective inhibitor with considerable potential for the treatment of certain hematologic malignancies.

Clinical significance of cadherin-6 expression in primary and recurrent epithelial ovarian cancer and its association with outcomes: A potential therapeutic target for epithelial ovarian cancer (206)

<b>Objectives:</b> Cadherin-6 (CDH6) is a membrane glycoprotein, and aberrant expression of CDH6 has been reported in several human carcinomas, suggesting a possible role in metastasis and invasion. Recently, antibody-drug conjugates (ADCs) targeting CDH6 have drawn attention to new cancer therapies and demonstrated their antitumor activity in preclinical models of epithelial ovarian cancer (EOC). However, limited data are available regarding the frequency of CDH6 expression and its relationship to clinical factors in EOC. Our goal was to understand the clinical significance of CDH6 expression in EOC. <b>Methods:</b> We performed immunohistochemical (IHC) staining on CDH6 expression in a total of 232 EOC surgical samples (including 181 primary tumors and 51 recurrent tumors). CDH6 IHC was performed using the Leica BOND III staining platform with an anti-CDH6 antibody (HPA007456, ATLAS ANTIBODIES). The CDH6 IHC scoring standard refers to the HER2 detection guidelines for gastric cancer (0, 1+, 2+, 3+). We define a score greater than or equal to 1 as positive for the expression of CDH6. <b>Results:</b> We investigated 181 patients with primary EOC for CDH6 expression through IHC. Total 117 (64.6%) patients tested positive. In which, 18 (15.4%), 84 (71.8%) and 15 (12.8%) cases were scored as 1+, 2+ and 3+, respectively. We then investigated the relationship between CDH6 expression and clinical-pathologic features in EOC. CDH6 expression was observed more frequently in high-grade serous carcinomas (89.0%, p < 0.0001), stage III/IV tumors (84.8%, p < 0.0001) and gross residual tumors in primary surgery (84.7%, p < 0.0001). CDH6-positive patients showed shorter progression-free survival (PFS) and overall survival (OS) (p < 0.0001 and p=0.0006) than that of CDH6-negative patients in all EOC patients. In addition, patients with CDH6 3+ had shorter PFS and OS than that of patients who had 0, 1+ and 2+ (p =0.028 and p=0.015) in the high-grade serous subgroup. We also investigated the expression of CDH6 in 51 recurrent EOC; 38/51 (74.5%) recurrent tumors tested positive for CDH6 expression, and nine (23.7%), 17 (44.7%) and 12 (31.6%) received scores of 1+, 2+ and 3+, respectively. CDH6 expression from recurrent tumors was observed in 18/24 (75.0%) high-grade serous, 11/16 (68.8%) clear cell, 4/5 (80.0%) endometrioid and 5/6 (83.3%) other histotypes. <b>Conclusions:</b> CDH6 expression is frequently observed in primary and recurrent EOC of all histotypes, especially in high-grade serous carcinoma. The frequency of CDH6 expression is consistent between primary and recurrent tumors. CDH6 is a promising therapeutic target for the treatment of EOC.

P1086: FAVEZELIMAB (ANTI–LAG-3) AND PEMBROLIZUMAB CO-BLOCKADE IN ANTI–PD-1–NAIVE PATIENTS WITH RELAPSED OR REFRACTORY CLASSICAL HODGKIN LYMPHOMA: AN OPEN-LABEL PHASE 1/2 STUDY

Background: Programmed cell death 1 (PD-1) inhibitors are a standard of care in patients with relapsed or refractory (R/R) classical Hodgkin lymphoma (cHL), but clinical interest persists for new approaches to deepen and lengthen responses. Dual blockade of PD-1 and lymphocyte-activation gene 3 (LAG-3) has demonstrated antitumor activity in preclinical models. Aims: The multicohort phase 1/2 MK-4280-003 study (NCT03598608) evaluated the safety and efficacy of favezelimab (MK-4280), a humanized Immunoglobulin G4 LAG-3 inhibitor, plus pembrolizumab (a PD-1 inhibitor) in patients with R/R hematologic malignancies. This analysis focused on anti–PD-1–naïve patients with R/R cHL (cohort 1). Methods: This study included a safety lead-in phase (part 1) to determine the recommended phase 2 dose (RP2D) followed by a dose-expansion phase (part 2). Eligible patients in cohort 1 must have had R/R cHL after autologous stem cell transplantation (ASCT) or been ineligible for ASCT and have had no prior anti–PD-1 therapy. In part 1, patients from all cohorts received intravenous (IV) pembrolizumab 200 mg every 3 weeks (Q3W) and favezelimab IV 200 mg or 800 mg Q3W. Dose-finding based on occurrence of dose-limiting toxicities (DLTs) was determined using a modified toxicity probability interval design. In part 2, patients received pembrolizumab + favezelimab at the established RP2D for up to 2 years (35 cycles), or until documented disease progression, adverse events (AEs), or withdrawal from the study. Primary end point was safety, including DLTs and AEs. Secondary end point was objective response rate (ORR). Duration of response (DOR), progression-free survival (PFS), and overall survival (OS) were exploratory end points. Results: Only 1 DLT (autoimmune hepatitis [grade 4]) was identified among the first 6 patients from all cohorts included in part 1 at the favezelimab 200 mg dose; thus, the dose was escalated to 800 mg. No DLTs were observed in the 15 additional patients treated at the 800 mg dose. The RP2D for the combination was defined as 800 mg Q3W + pembrolizumab 200 mg Q3W. In cohort 1, 30 patients were enrolled; median age was 40 years, 53% had ECOG PS 0, and 80% had no more than 3 prior lines of therapy. As of the database cutoff (Nov 1, 2021), 9 of 30 (30%) patients had discontinued treatment either due to adverse events (n=3) or disease progression (n=6). After a median follow-up of 13.5 months, ORR for cohort 1 was 73% (95% CI, 54-88; complete response, 7 patients [23%]; partial response, 15 patients [50%]). 28 of 30 patients (93%) had a reduction from baseline in target lesions. Median DOR was not reached ([NR]; 95% CI, 0+ to 23+ months) and 6 patients (51%) had response ≥12 months. The median PFS was 19 months (95% CI, 8-NR) and the 12-month PFS rate was 57%. The median OS was NR (95% CI, NR-NR) and the 12-month OS rate was 94%. Treatment-related AEs (TRAE) occurred in 26 patients (87%); most common (≥10%) were hypothyroidism (27%), fatigue (20%), infusion-related reactions (20%), headache (17%), and arthralgia, hyperthyroidism, myalgia, and nausea (10% each). Grade 3 or 4 TRAEs occurred in 6 patients (20%) and 10% of patients discontinued due to TRAEs. No treatment-related deaths occurred. Summary/Conclusion: Favezelimab 800 mg + pembrolizumab 200 mg Q3W demonstrated an acceptable safety profile and effective antitumor activity in anti–PD-1–naïve patients with R/R cHL. Further studies are merited to compare the activity of this combination to that of pembrolizumab alone.

P1087: FAVEZELIMAB (ANTI–LAG-3) AND PEMBROLIZUMAB CO-BLOCKADE IN PATIENTS WITH RELAPSED OR REFRACTORY CLASSICAL HODGKIN LYMPHOMA WHO PROGRESSED AFTER ANTI–PD-1 THERAPY: AN OPEN-LABEL PHASE 1/2 STUDY

Background: PD-1 inhibitors are a standard of care for relapsed or refractory (R/R) classical Hodgkin lymphoma (cHL), but optimal therapy is yet to be defined for patients whose disease progresses after anti–PD-1 treatment. Dual blockade of PD-1 and lymphocyte-activation gene 3 (LAG-3) has demonstrated antitumor activity in preclinical models. Aims: This multicohort phase 1/2 study (NCT03598608) evaluated safety and efficacy of favezelimab (MK-4280), a humanized IgG4 LAG-3 inhibitor, plus the PD-1 inhibitor pembrolizumab in patients with R/R hematologic malignancies. Cohort 2 focused on patients with R/R cHL refractory to anti–PD-1 therapy. Methods: This study included a safety lead-in phase (part 1) to determine recommended phase 2 dose (RP2D) followed by a dose-expansion phase (part 2). Eligible patients in cohort 2 had R/R cHL, relapsed after or were ineligible for autologous stem cell transplantation (ASCT), and progressed after ≥2 doses of anti–PD-1 therapy (within 12 weeks of last dose). In part 1, patients from all cohorts received intravenous (IV) pembrolizumab 200 mg every 3 weeks (Q3W) and favezelimab IV 200 mg or 800 mg Q3W. Dose-finding based on occurrence of dose-limiting toxicities (DLT) was determined using a modified toxicity probability interval design. In part 2, patients received pembrolizumab + favezelimab at the established RP2D for up to 2 years (35 cycles), or until documented disease progression, adverse events (AEs), or withdrawal from study. Primary end point was safety, including DLTs and AEs. Secondary end point was objective response rate (ORR). Duration of response (DOR), progression-free survival (PFS), and overall survival (OS) were exploratory end points. Results: Only 1 DLT (autoimmune hepatitis [grade 4]) was observed among the first 6 patients from all cohorts included in part 1 at the favezelimab 200 mg dose; thus, the dose was escalated to 800 mg. No DLTs were observed in the 15 additional patients at the 800 mg dose. Favezelimab RP2D was defined as 800 mg Q3W + pembrolizumab 200 mg Q3W. In cohort 2, 33 patients were enrolled; median age was 37 years, 64% had ECOG PS 0, and 94% had at least 4 prior lines of therapy. At database cutoff (Nov 1, 2021), 20 patients had discontinued treatment due to adverse events (n=7); disease progression or clinical progression (n=11); or withdrawal/physician decision (n=2). After a median follow-up of 16.5 months, ORR for patients receiving favezelimab 800 mg (n=29) was 31% (95% CI, 15-51; complete response, 2 [7%]; partial response, 7 [24%]). 19 of 29 responders (66%) had an anti–PD-1–based regimen as their most recent line of therapy at study entry. 23 of 29 patients (79%) had a reduction from baseline in target lesions. Median DOR for patients who received favezelimab 800 mg was not reached ([NR]; 95% CI, 0+ to 14+ months). For all patients in cohort 2, the median PFS was 9 months (95% CI, 5-15); 12-month PFS rate was 39%. Median OS was 26 months (95% CI, 26-NR); 12-month OS rate was 91%. Treatment-related AEs (TRAE) occurred in 28 patients (85%); most common (>10%) were hypothyroidism (18%), nausea and fatigue (15% each), and arthralgia and diarrhea (12% each). Grade 3 or 4 TRAEs occurred in 6 patients (18%) and 18% of patients discontinued treatment due to TRAEs. No treatment-related deaths occurred. Summary/Conclusion: Favezelimab 800 mg + pembrolizumab 200 mg Q3W showed a tolerable safety profile and effective antitumor activity in heavily pretreated patients with R/R cHL whose disease had progressed after anti–PD-1 therapy, suggesting that the combination may reinduce a response in these patients.

Abstract 2155: PMR-116, a novel inhibitor of ribosome biogenesis with antitumor activity in preclinical models of prostate cancer

Abstract Advanced prostate cancer is characterised by mutations and amplifications of genes involved in regulating protein synthesis. PTEN-loss stimulates activity of the mTOR pathway, while amplification of MYC leads to increased ribosome biogenesis and elevated mRNA translation rate. Our previous work has demonstrated the efficacy of co-targeting ribosome biogenesis, via inhibition of RNA Pol I activity, and 4E-BP1 phosphorylation to suppress prostate cancer growth in vivo in GEMM of PCa and in patient-derived xenografts (Rebello et al., Clinical Cancer Research, 2016; Lawrence et al., European Urology, 2018). In a collaboration with Pimera Inc., we investigated the efficacy of their new lead RNA Pol I inhibitor PMR-116 in models of prostate cancer. PMR-116 is well tolerated in vivo in mice and can be given at 300mg/kg weekly. Using the Hi-MYC mouse model of PCa we show that dosing 6 month old mice once weekly for 4 weeks can decrease the incidence of invasive lesions by up to 85% compared to vehicle control while reverting glands to patterns of low grade intraepithelial neoplasia. PMR-116 rapidly inhibits proliferation in the Hi-MYC model with a 50% decrease in Ki67 observed 12 hours after oral administration. Conversely, PMR-116 showed minimal anti-tumour efficacy in the PTEN-null model of PCa suggesting that elevated MYC signalling may be required for optimal response. To further validate our promising GEMM results in more clinically relevant human-derived models, we used patient-derived xenografts lines we established from multidrug-resistant, metastatic PCa (Lawrence et al, European Urology, 2018). PMR-116 treatment decreased tumour volume in all PDX tested including complete response in a line in which tumour volume decreased by ~90% compared to baseline. We believe this new RNA Pol I inhibitor shows promising results in a wide range of preclinical models and may exert higher efficacy in tumours expressing high levels of MYC. PMR-116 is currently in Phase I dose escalation trial in patient with solid tumours (ACTRN12620001146987). Citation Format: Alisee Huglo, Richard Rebello, Mitchell Lawrence, Gail Risbridger, Denis Drygin, Mustapha Haddach, Katherine Hannan, Ross Hannan, Luc Furic. PMR-116, a novel inhibitor of ribosome biogenesis with antitumor activity in preclinical models of prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2155.

Abstract 3928: The pan-CLK/DYRK inhibitor cirtuvivint selectively disrupts alternative splicing and has broad anti-tumor activity in preclinical models

Abstract Dysregulated alternative pre-mRNA splicing (AS) is commonly associated with human malignancies, producing pathological proteomes that underlie disease initiation, progression, and therapeutic resistance. The CDC2-like kinases (CLKs) and dual-specificity tyrosine-regulated kinases (DYRKs) are thought to govern AS efficiency and specificity by directly phosphorylating splicing factors that influence pre-mRNA splice junction selection. Cirtuvivint (SM08502) is a first-in-class small molecule ATP-competitive inhibitor of CLK/DYRK kinases. To evaluate the contribution of these kinases to AS profiles, high-depth RNAseq analysis was performed across 39 tumor cell lines (representing 9 lineages) and compared to 6 non-cancerous cell lines after treatment with cirtuvivint. Both baseline and drug-induced changes in AS events (ASEs) were measured using a multivariate analysis of transcript splicing (rMATS). Pan-CLK/DYRK inhibition was found to affect a minority of baseline ASEs, leaving the majority of spliceosome activity intact in all samples; however, the magnitude and quantity of detected drug-induced alterations were larger in tumor compared to non-cancerous cell lines. The majority of ASEs resulting from pan-CLK/DYRK inhibition were enriched for exon skipping events and were tumor type-specific. Moreover, drug-induced ASEs were significantly associated with disease-promoting biology across lineage and oncogenic driver contexts, including perturbed splicing of the AR-V7 variant in treatment-resistant prostate cancer and MDM2 in p53 wild-type cancers.To assess the breadth and depth of CLK/DYRK dependencies in human cancers, the effects of pan-CLK/DYRK inhibition on growth and survival of 154 cancer cell line models, 46 PDX models, and 43 CDX models were tested. EC50s in cell viability assays ranged from 0.014 to 0.73 μM in culture with strong effects observed in subsets of cell lines across all lineages tested. Multiomic data integration revealed sensitivity to cirtuvivint was associated with alterations in splicing genes. In vivo, tumor growth inhibition studies testing cirtuvivint at exposures ~2X below the MTD resulted in significant disease control (≥50% TGI) in 38/46 PDX and 38/43 CDX models. These observations indicate broad cancer relevance, at least in the preclinical setting, and expose vulnerabilities to CLK-DYRK-regulated splicing that can potentially be therapeutically addressed with pan CLK/DYRK inhibitors. Citation Format: Elizabeth A. McMillan, Carine Bossard, Emily Creger, Carsten Merkwirth, Raffaella Pippa, Matthew Jarvis, Krishna Sriram, Melinda Pedraza, Maureen Ibanez, Deepti Bhat, Carolyn Lai, Josh Stewart, Brian Eastman, Chi-Ching Mak, Michael A. White, Darrin Beaupre. The pan-CLK/DYRK inhibitor cirtuvivint selectively disrupts alternative splicing and has broad anti-tumor activity in preclinical models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3928.

Abstract 1509: Genome-wide CRISPR/Cas9 library screening identified THRAP3 as a critical driver for resistance to ATR inhibitor in sarcomas revealing synthetic lethality with ATM inhibition

Abstract Background: ATR plays a crucial role in maintaining genomic integrity by responding to a large spectrum of DNA damage, including double strand breaks (DSBs) that interfere with replication. We have previously demo started that ATR inhibition is associated with anti-tumor activity in pre-clinical models of soft-tissue sarcomas (STS) (Laroche et al., 2020). We decided to investigate the mechanisms of resistance to ATR inhibition in sarcomas. Methods: We used a CRISPRa was to identify genes that mediate resistance to AZD6738 in STS cells. The anti-tumor activity of AZD6738 (ATR inhibitor) and AZD0156 (ATM inhibitor) was investigated in a panel for 10 STS cell lines and two patient-derived xenografts (PDX) established at Institut Bergonié (Bordeaux, France). Results: We used a CRISPR approach in a STS cell line resistant to AZD6738 and we made a negative-selection screen, to identify genes whose silencing conferred sensitivity to low doses of ATR inhibition. Among these genes, we identified THRAP3 which encodes a protein phosphorylated in response to DNA damage and primarily by ATR. THRAP3 is involved in the maturation and further export of transcripts encoding the ATM and its depletion results in deficient processing of transcripts encoding the ATM kinase. We validate the result of our CRISPR analysis by demonstrating that selective THRAP3 inhibition reduce significantly ATRi IC50. Given the role of role of THRAP3 on the regulation of ATM activity, we decided to investigate the potential synergy between ATR and ATM inhibition in vivo and in vitro. AZD6738 and AZD0156 displayed a synergistic or additive effect in above all the STS cell lines tested. We noted that ATRi treatment reduced phosphorylation of the ATR kinase target CHK1 but increased ATM phosphorylation, suggesting that ATM pathway takes over for DNA Damage Response and cells survival. In contrast, both ATR and ATM pathway were inhibited when AZD6738 and AZD0156 were used in combination, as shown by reduction of CHK1 and ATM phosphorylation. We validated our in vitro results in an in vivo model of liposarcoma xenograft in which AZD6738 and AZD0156 had synergistic anti-tumor activity. Conclusion: Our study demonstrates synthetically lethal interactions between ATM and ATR in vitro and in vivo. This combination deserves further investigaitons in sarcomas. Citation Format: Mariella Spalato, Audrey Laroche-Clary, Vanessa Chaire, Antoine Italiano. Genome-wide CRISPR/Cas9 library screening identified THRAP3 as a critical driver for resistance to ATR inhibitor in sarcomas revealing synthetic lethality with ATM inhibition [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1509.

Abstract 1766: SGN-ALPV a novel, investigational vedotin ADC demonstrates highly effective targeting of oncofetal phosphatases ALPP and ALPPL2 in preclinical models

Abstract Antibody-drug conjugates (ADC) leverage the specificity of antibodies to direct the delivery of potent cytotoxic agents to cancer cells. To fully leverage this specificity, targets with significant differential tumor versus normal tissue expression are ideal for ADC development. Placental alkaline phosphatases, ALPP and ALPPL2, are proteins present during fetal development but are found in several tumor types, making them an attractive ADC target. These cell membrane-attached phosphatases form homo- and heterodimers and play key roles in nucleotide recycling. SGN-ALPV is a novel investigational vedotin ADC comprised of a humanized IgG1 monoclonal antibody conjugated to the microtubule disrupting agent monomethyl auristatin E (MMAE) via a protease-cleavable peptide linker that has been clinically validated in multiple ADC programs. Here we characterize the target antigens, ALPP and ALPPL2, and evaluate SGN-ALPV antitumor activity in preclinical models. Immunohistochemistry and genomic data mining showed that ALPP and ALPPL2 have a highly restricted normal tissue expression yet high expression in several solid tumor types including ovarian, endometrial, germ cell, non-small cell lung and gastric carcinomas. Importantly, normal tissue expression is restricted to placenta and reproductive tissue, with low levels in lung tissue. SGN-ALPV utilizes a humanized antibody, h12F3, that is highly specific for both human and cynomolgus monkey ALPP and ALPPL2 proteins, but not other related phosphatases. In vitro, upon binding to SGN APLV, the antigens, ALPP and ALPPL2, are internalized to lysosomal vesicles releasing the MMAE payload, whose cytotoxic features drive mitotic arrest, apoptosis, and the induction of immunogenic cell death. Additionally, SGN-ALPV mediates antibody dependent cellular cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP) in vitro but lacks complement-dependent cytotoxicity. In preclinical studies, SGN-ALPV exhibits robust antitumor activity in cell line- and patient-derived xenograft models of ovarian, lung, pancreatic, and gastric carcinoma including models with both homogenous and heterogeneous expression of ALPP and ALPPL2, consistent with robust bystander activity of vedotin ADCs. Although, the contribution of ADCC and ADCP in vivo is currently unknown, it is expected that the antitumor activity of SGN-ALPV is mediated by MMAE cytotoxicity. SGN-ALPV was well tolerated in non-human primates (NHP) and exhibited linear pharmacokinetic characteristics, with a toxicity profile consistent with other vedotin-based ADCs. In summary, differential expression of ALPP and ALPPL2 in the tumor versus normal tissue, antibody specificity, antitumor activity, and tolerability of SGN-ALPV provide a strong rationale for the initiation of a planned first-in-human Phase 1 clinical study. Citation Format: Sarah Anderson, Nanna Hansen, Robert Lawrence, Aroon T. Chande, David Ortiz, Christopher Carosino, Esther Trueblood, Nicole Stevens, Kerry Klussman, Angela Epp, Bill Arthur, Shyra Gardai, Hector Rincon. SGN-ALPV a novel, investigational vedotin ADC demonstrates highly effective targeting of oncofetal phosphatases ALPP and ALPPL2 in preclinical models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1766.

A first-in-human phase 1/2 study of FGF401 and combination of FGF401 with spartalizumab in patients with hepatocellular carcinoma or biomarker-selected solid tumors

BackgroundDeregulation of FGF19-FGFR4 signaling is found in several cancers, including hepatocellular carcinoma (HCC), nominating it for therapeutic targeting. FGF401 is a potent, selective FGFR4 inhibitor with antitumor activity in preclinical models. This study was designed to determine the recommended phase 2 dose (RP2D), characterize PK/PD, and evaluate the safety and efficacy of FGF401 alone and combined with the anti-PD-1 antibody, spartalizumab.MethodsPatients with HCC or other FGFR4/KLB expressing tumors were enrolled. Dose-escalation was guided by a Bayesian model. Phase 2 dose-expansion enrolled patients with HCC from Asian countries (group1), non-Asian countries (group2), and patients with other solid tumors expressing FGFR4 and KLB (group3). FGF401 and spartalizumab combination was evaluated in patients with HCC.ResultsSeventy-four patients were treated in the phase I with single-agent FGF401 at 50 to 150 mg. FGF401 displayed favorable PK characteristics and no food effect when dosed with low-fat meals. The RP2D was established as 120 mg qd. Six of 70 patients experienced grade 3 dose-limiting toxicities: increase in transaminases (n = 4) or blood bilirubin (n = 2). In phase 2, 30 patients in group 1, 36 in group 2, and 20 in group 3 received FGF401. In total, 8 patients experienced objective responses (1 CR, 7 PR; 4 each in phase I and phase II, respectively). Frequent adverse events (AEs) were diarrhea (73.8%), increased AST (47.5%), and ALT (43.8%). Increase in levels of C4, total bile acid, and circulating FGF19, confirmed effective FGFR4 inhibition.Twelve patients received FGF401 plus spartalizumab. RP2D was established as FGF401 120 mg qd and spartalizumab 300 mg Q3W; 2 patients reported PR.ConclusionsAt biologically active doses, FGF401 alone or combined with spartalizumab was safe in patients with FGFR4/KLB-positive tumors including HCC. Preliminary clinical efficacy was observed. Further clinical evaluation of FGF401 using a refined biomarker strategy is warranted.Trial registrationNCT02325739.

A phase 1 trial of RP2, a first-in-class, enhanced potency oncolytic HSV expressing an anti-CTLA-4 antibody as a single agent and combined with nivolumab in patients with advanced solid tumors.

TPS2704 Background: RP2 is a selective replication-competent herpes simplex virus 1 (HSV-1) that contains a codon-optimized sequence for human granulocyte-macrophage colony-stimulating factor (GM-CSF), the gibbon ape leukemia virus surface glycoprotein (GALV-GP) with the R- sequence deleted (R-), GM-CSF, and an anti–cytotoxic T lymphocyte antigen 4 (CTLA-4) antibody-like molecule. These modifications are intended to increase oncolytic potency, cell-to-cell spread, tumor antigen release, and systemic anti-tumor immune activation. RP2 has demonstrated antitumor activity in preclinical models using viruses similar to RP2 expressing murine versions of anti-CTLA-4 and GM-CSF, both alone and in combination with PD1-1 blockade. Methods: This is a Phase 1 multicenter, open-label, study evaluating RP2 ± nivolumab (NCT04336241). Part 1 evaluated escalating doses of monotherapy RP2 with a modified 3 + 3 design. Patients (pts) received intratumoral (IT) injections of up to 10 mL of RP2 into superficial or visceral tumors Q2W x5 across two dose levels (DL1: 105 plaque-forming units (PFU)/mL once, then followed by 106 PFU/mL x4; DL 2: 106 PFU/mL once, then followed by 107 PFU/mL x4). The recommended Phase 2 dose of RP2 was identified as 106 PFU/mL once, followed by subsequent doses of 1 × 107 PFU/mL. In Part 2, up to 60 evaluable pts will be enrolled, including 30 pts in Cohort 2a and 30 in Cohort 2b. Cohort 2a was designed to evaluate the safety and antitumor activity of the combination in pts with solid tumors, and is fully enrolled. Cohort 2b is open for enrollment of pts with advanced or metastatic uveal melanoma, NSCLC, breast cancer, head and neck cancer or GI cancers (NSCLC, breast or GI cancers must have at least one liver tumor suitable for injection). Pts in Part 2 receive intra-tumoral RP2 at the RP2D Q2W for up to 8 doses in combination with 240 mg nivolumab IV Q2W or 480 mg nivolumab IV Q4W for up to two years from the first RP2 dose. In Part 3 (not yet open for enrollment), up to 15 evaluable pts are able to be enrolled to evaluate RP2 monotherapy including at least 10 pts with NSCLC, breast or GI cancers with at least one liver tumor suitable for injection. Reinitiation of up to 8 additional RP2 doses is permitted if prespecified criteria are met. Pts are dosed with RP2 by direct visualization or ultrasound-guided injection into superficial, subcutaneous, or nodal tumors and by image-guided injection into deeper lesions, including visceral lesions. Key inclusion criteria include histologically confirmed advanced or metastatic non-neurological solid tumors, at least one measurable and injectable tumor of diameter ≥1 cm, ECOG ≤1, and adequate hematologic, hepatic, and renal function. Exclusion criteria include prior treatment with oncolytic viruses, acute or chronic hepatitis B or C infection, and HIV infections. Clinical trial information: NCT04336241.

Glypican-3-specific CAR-NKT cells overexpressing BATF3 mediate potent antitumor activity against hepatocellular carcinoma.

e14521 Background: Hepatocellular carcinoma (HCC), the fourth leading cause of cancer-related deaths worldwide, is amenable to immunotherapies that target glypican-3 (GPC3), a protein expressed by over 75% of HCCs but not by healthy tissues. The invariant natural killer T cells (NKTs) prevent HCC tumorogenesis through interactions with the gut microbiome in mice, and the presence of tumor-infiltrating NKTs is associated with improved clinical outcomes. We previously tested GPC3-specific chimeric antigen receptors (CARs) and selected a receptor with both CD28 and 41BB costimulatory endodomains based on its ability to mediate superior antitumor activity of transduced NKTs in vivo. Co-expression of interleukin-15 (IL15), a cytokine that supports NKT expansion and persistence, with the chosen GPC3-CAR further enhanced this activity. GPC3-CAR NKTs co-expressing IL15 (15.GPC3-CAR) overexpressed the Basic Leucine Zipper ATF-Like Transcription Factor 3 (BATF3), a member of the AP-1 family. Since AP-1 family proteins are master regulators of cell survival and proliferation, we hypothesized that overexpressing BATF3 in GPC3-CAR NKTs (BATF3.GPC3-CAR) will lead to superior expansion, persistence, and antitumor activity compared to 15.GPC3-CAR NKTs. Methods: We used RNAseq and flow cytometry to define the transcriptomic and phenotypic characteristics, respectively, of BATF3-overexpressing NKTs at baseline and after tumor cell killing in co-culture. We also used co-culture assays to evaluate the ability of BATF3- or IL15-expressing NKTs to proliferate, produce effector cytokines, and kill tumor cells after multiple rounds of exposure. Finally, we evaluated the ability of BATF3.GPC3-CAR and IL15.GPC3-CAR NKTs to expand, persist, and target tumors in an HCC xenograft murine model. Results: BATF3 overexpression in NKTs induced significant differences in gene expression profiles compared to a GFP control at baseline (DEGs up: 20; down: 26, p &lt; 0.01) and after tumor cell killing (DEGs up: 19; down: 32; p &lt; 0.01; fold change &gt; 2 or &lt; 0.5, respectively) corresponding to enrichment of gene sets related to metabolic fitness. Importantly, CD62L+ NKTs, which have enhanced antitumor properties, were enriched in BATF3-expressing NKTs (27.6% vs 8.2%, p &lt; 0.05, versus GFP control). Further, BATF3 significantly enhanced NKT proliferation (area under the curve of absolute NKT cell counts: 5x1011 vs 1.1x1011, p = 0.001; fold expansion: 6.12x104 vs 1.2x104, p = 0.001, versus IL15 NKTs). Finally, BATF3.GPC3-CAR NKTs induced long-term tumor control and significantly improved survival of HCC xenograft-bearing mice compared to 15.GPC3-CAR NKTs (p = 0.0002, Mantel-Cox analysis). Conclusions: BATF3.GPC3-CAR NKTs induce robust antitumor activity in pre-clinical models of HCC. These results provide a foundation for evaluating BATF3.GPC3-CAR NKTs in patients with relapsed/refractory HCC.

An open-label, multicenter, phase 1 study of RP3 as a single agent and in combination with nivolumab in patients (pts) with solid tumors.

TPS2705 Background: RP3 is a genetically modified herpes simplex virus 1 (HSV-1) that contains insertions for the gibbon ape leukemia virus surface glycoprotein (GALV-GP) with the R- sequence deleted (R-), an anti–cytotoxic T lymphocyte antigen 4 (CTLA-4) antibody-like molecule, CD40 ligand, and 4-1BB ligand. Together, these insertions are expected to increase oncolytic potency, cell-to-cell spread, immunogenic cell death, and systemic immune activation. RP3 has demonstrated antitumor activity in preclinical models using viruses similar to RP3 expressing murine versions of anti-CTLA-4, CD40L, and 4-1BBL both alone and in combination with PD1-1 blockade. Methods: This is an open-label, multicenter, Phase 1 study evaluating RP3 as monotherapy or in combination with nivolumab (nivo) in patients (pts) with solid tumors (NCT04735978). Part 1 evaluated escalating doses of RP3. Pts in Part 1 received IT injections of up to 10 mL RP3 into superficial, nodal, or visceral lesions Q2W x 5 across two dose levels (DL1: 105 plaque-forming units (PFU)/mL once, then 106 PFU/mL x 4; DL2: 106 PFU/mL once, then 107 PFU/mL x4). The RP2D is 106 PFU/mL once, followed by 107 PFU/mL IT Q2W. In Part 2, pts are being enrolled into expansion cohorts of 45 patients with GI (including HCC), lung, breast, and squamous cell carcinoma of the head and neck treated with RP1 combined with nivo. Additional cohorts will enroll patients treated with RP3 followed by nivo, RP3 monotherapy to further explore biomarkers in injected and uninjected tumors, and with the potential to also open a cohort in melanoma. Pts in both Part 1 and Part 2 may receive up to 8 additional doses of RP3 if protocol-specified criteria are met. Key inclusion criteria: confirmed advanced or metastatic non-neurological solid tumors, at least one measurable tumor ≥ 1 cm and injectable tumors ≥ 1 cm in aggregate, ECOG ≤1, and adequate hematologic, hepatic, and renal function. In Cohorts 1, 2, and 4, approximately 50% of the pts with lung, breast, and GI cancer must have liver lesions intended for injection. Exclusion criteria include prior oncolytic virus treatment, need for immunosuppressive therapy, an autoimmune disease requiring systemic therapy, active significant herpetic infections or prior complications of HSV-1 infection, active or chronic HBV or HCV infection, known HIV infection, or prior active malignancy within 3 years. Clinical trial information: NCT04735978.

The bi-steric mTORC1-selective inhibitor RMC-5552 in tumors with activation of mTOR signaling: Preclinical activity in combination with RAS(ON) inhibitors in RAS-addicted tumors, and initial clinical findings from a single agent phase 1/1b study.

3098 Background: RMC-5552 is a potent bi-steric mTORC1-selective inhibitor that activates the downstream tumor suppressor 4EBP1, thereby inhibiting initiation of protein translation. This novel therapeutic moiety addresses a key limitation of rapalogs, which do not effectively inhibit phosphorylation of 4EBP1. RMC-5552 has previously demonstrated significant anti-tumor activity in preclinical models of human cancers with mTOR pathway activation. Additionally, mTOR signaling plays a key role in therapeutic response and resistance in RAS-addicted cancers, which represent a significant unmet medical need. Methods: We examined the combination of bi-steric mTORC1 inhibitors (RMC-5552 and the research tool compound RMC-6272) with direct inhibitors of active RAS (RAS(ON) inhibitors) in mutant KRAS-driven models. To enable the clinical testing of RMC-5552 as a companion inhibitor for RAS(ON) inhibitors, a Phase 1/1b dose-escalation trial of RMC-5552 monotherapy is currently testing a once-a-week IV schedule. Results: RMC-5552 and RMC-6272 demonstrated marked combinatorial anti-tumor activity with RAS(ON) inhibitors across a series of preclinical models of KRAS mutated non-small cell lung cancer. The combination enhanced tumor apoptosis and resulted in durable tumor regressions as compared to tumor growth inhibition resulting from single agents alone. As of 13 January 2022, a total of 14 patients with solid tumors have been evaluated in an ongoing Phase 1/1b trial over 5 dose levels ranging from 1.6 to 12 mg IV weekly. Median age was 62 years and the majority received ≥3 prior therapies. The most common (&gt; 25%) drug-related adverse events were mucositis/stomatitis (43%) and decreased appetite (29%). The most common grade 3 drug-related adverse events were mucositis/stomatitis observed in 3 patients in dose levels ≥ 10 mg (21%) and were dose-limiting. The dose of 6 mg IV weekly was well tolerated. Plasma exposures of RMC-5552 were dose-proportionate at lower dose levels up to 6 mg but increased above dose proportionality with higher dose levels. Plasma exposures at 6 mg and above were consistent with those resulting in inhibition of tumor p4EBP1 in preclinical models. Of 5 patients evaluable for efficacy at doses of 6 mg and higher, one confirmed PR was observed in a patient with head and neck cancer with a pathogenic mutation in PTEN (ORR 20%) and 3 patients had a best response of SD. Dose-optimization is ongoing. Conclusions: RMC-5552 is clinically active in tumors with mTORC1 signaling activation at a tolerable dose and schedule and has the potential to be a companion inhibitor of choice for RAS(ON) inhibitors in RAS-addicted tumors. Clinical trial information: NCT04774952.

Favezelimab (anti–LAG-3) plus pembrolizumab in patients with anti–PD-1–naive relapsed or refractory (R/R) classical Hodgkin lymphoma (cHL): An open-label phase 1/2 study.

7516 Background: PD-1 inhibitors are a standard of care in pts with R/R cHL but new approaches are still needed to deepen and lengthen responses. Dual blockade of PD-1 and LAG-3 has demonstrated antitumor activity in preclinical models. The multicohort phase 1/2 MK-4280-003 study (NCT03598608) evaluated the safety and efficacy of favezelimab (MK-4280), a humanized IgG4 LAG-3 inhibitor, plus pembrolizumab (pembro; a PD-1 inhibitor) in pts with R/R hematologic malignancies. This analysis focused on anti–PD-1–naïve pts with R/R cHL (cohort 1). Methods: This study included a safety lead-in phase (part 1) to determine the recommended phase 2 dose (RP2D) followed by a dose-expansion phase (part 2). Eligible pts in cohort 1 must have R/R cHL after autologous stem cell transplantation (ASCT) or be ineligible for ASCT and have had no prior anti–PD-1 therapy. In part 1, patients from all cohorts received pembro IV 200 mg Q3W and favezelimab IV 200 mg or 800 mg Q3W. Dose escalation followed the mTPI design. In part 2, pts received pembro + favezelimab at the established RP2D for up to 35 cycles. Primary end point was safety. Secondary end point was ORR. DOR, PFS, and OS were exploratory end points. Results: Only 1 dose-limiting toxicity (DLT; autoimmune hepatitis [grade 4]) was identified among the first 6 pts from all cohorts in part 1 at the favezelimab 200 mg dose; thus, the dose was escalated to 800 mg. No DLTs were observed in the 15 additional pts treated at the 800 mg dose. The RP2D for the combination was defined as 800 mg Q3W + pembro 200 mg Q3W. In cohort 1, 30 pts were enrolled; median age was 40 years, 53% had ECOG PS 0, and 80% had ≤3 prior lines of therapy. After a median follow-up of 13.5 mo, ORR for cohort 1 was 73% (95% CI, 54-88; CR, 7 pts [23%]; PR, 15 pts [50%]). 28 of 30 pts (93%) had reduction from baseline in target lesions. Median DOR was not reached (NR; 95% CI, 0+ to 23+ mo); 6 pts (51%) had response ≥12 mo. Median PFS was 19 mo (95% CI, 8-NR); 12-mo PFS rate was 57%. Median OS was NR (95% CI, NR-NR); 12-mo OS rate was 94%. As of the database cutoff (Nov 1, 2021), 9 of 30 pts had discontinued (3 AEs; 6 PD). Treatment-related AEs (TRAE) occurred in 26 pts (87%); most common (≥10%) were hypothyroidism (27%), fatigue (20%), infusion-related reactions (20%), headache (17%), and arthralgia, hyperthyroidism, myalgia, and nausea (10% each); grade 3 or 4 TRAEs occurred in 6 pts (20%). 10% of pts discontinued due to TRAEs. No treatment-related deaths occurred. Conclusions: Favezelimab 800 mg + pembrolizumab 200 mg Q3W demonstrated a tolerable safety profile and effective antitumor activity in pts with anti–PD-1–naïve R/R cHL. Further studies will be useful to compare its activity to that of pembrolizumab alone. Clinical trial information: NCT03598608.

Favezelimab (anti–LAG-3) plus pembrolizumab in patients with relapsed or refractory (R/R) classical Hodgkin lymphoma (cHL) after anti–PD-1 treatment: An open-label phase 1/2 study.

7545 Background: PD-1 inhibitors are a standard of care for R/R cHL but optimal therapy after anti–PD-1 therapy failure is yet to be defined. LAG-3/PD-1 coblockade has demonstrated antitumor activity in preclinical models. This multicohort phase 1/2 study (NCT03598608) evaluated the safety and efficacy of favezelimab (MK-4280), a humanized IgG4 LAG-3 inhibitor, plus the PD-1 inhibitor pembrolizumab (pembro) in pts with R/R hematologic malignancies. Cohort 2 focused on pts with R/R cHL refractory to anti–PD-1 therapy. Methods: This study included a safety lead-in phase (part 1) to determine recommended phase 2 dose (RP2D) followed by a dose-expansion phase (part 2). Eligible pts in cohort 2 had R/R cHL, relapsed after or were ineligible for autologous stem cell transplantation (ASCT), and progressed after ≥2 doses of anti–PD-1 therapy (within 12 weeks of last dose). In part 1, pts from all cohorts received pembro IV 200 mg Q3W and favezelimab IV 200 mg or 800 mg Q3W. Dose-finding based on occurrence of dose-limiting toxicities (DLT) was determined using an mTPI design. In part 2, pts received pembro + favezelimab at the established RP2D for up to 35 cycles. Primary end point was safety. Secondary end point was ORR. DOR, PFS, and OS were exploratory. Results: Only 1 DLT (autoimmune hepatitis [grade 4]) was observed among the first 6 pts from all cohorts in part 1 at the favezelimab 200 mg dose; thus, the dose was escalated to 800 mg. No DLTs were observed in 15 additional pts at the 800 mg dose. Favezelimab RP2D was defined as 800 mg Q3W + pembro 200 mg Q3W. In cohort 2, 33 pts were enrolled; median age was 37 yrs, 64% had ECOG PS 0, and 94% had ≥4 prior lines of therapy. After a median follow-up of 16.5 mo, ORR for pts receiving favezelimab 800 mg (n = 29) was 31% (95% CI, 15-51; CR, 2 [7%]; PR, 7 [24%]); 66% of responders had an anti–PD-1–based regimen as most recent line of therapy at study entry. 23 of 29 pts (79%) had reduction from baseline in target lesions. Median DOR for pts who received favezelimab 800 mg was not reached (NR; 95% CI, 0+ to 14+ mo). For all pts in cohort 2, median PFS was 9 mo (95% CI, 5-15); 12-mo PFS rate was 39%. Median OS was 26 mo (95% CI, 26-NR); 12-mo OS rate was 91%. At database cutoff (Nov 1, 2021), 20 pts discontinued treatment (7 AEs, 11 PD/clinical progression, 2, withdrawal/physician decision). TRAEs occurred in 28 pts (85%); most common ( &gt; 10%) were hypothyroidism (18%), nausea and fatigue (15% each), and arthralgia and diarrhea (12% each); grade 3 or 4 TRAEs occurred in 6 pts (18%); 18% discontinued treatment due to TRAEs. No treatment-related deaths occurred. Conclusions: Favezelimab 800 mg + pembro 200 mg Q3W showed a tolerable safety profile and effective antitumor activity in heavily pretreated pts with R/R cHL whose disease had progressed after anti–PD-1 therapy, suggesting that the combination may reinduce a response in these pts. Clinical trial information: NCT03598608.

Mobilization of innate and adaptive antitumor immune responses by the RNP-targeting antibody ATRC-101

Immunotherapy approaches focusing on T cells have provided breakthroughs in treating solid tumors. However, there remains an opportunity to drive anticancer immune responses via other cell types, particularly myeloid cells. ATRC-101 was identified via a target-agnostic process evaluating antibodies produced by the plasmablast population of B cells in a patient with non-small cell lung cancer experiencing an antitumor immune response during treatment with checkpoint inhibitor therapy. Here, we describe the target, antitumor activity in preclinical models, and data supporting a mechanism of action of ATRC-101. Immunohistochemistry studies demonstrated tumor-selective binding of ATRC-101 to multiple nonautologous tumor tissues. In biochemical analyses, ATRC-101 appears to target an extracellular, tumor-specific ribonucleoprotein (RNP) complex. In syngeneic murine models, ATRC-101 demonstrated robust antitumor activity and evidence of immune memory following rechallenge of cured mice with fresh tumor cells. ATRC-101 increased the relative abundance of conventional dendritic cell (cDC) type 1 cells in the blood within 24 h of dosing, increased CD8+ T cells and natural killer cells in blood and tumor over time, decreased cDC type 2 cells in the blood, and decreased monocytic myeloid-derived suppressor cells in the tumor. Cellular stress, including that induced by chemotherapy, increased the amount of ATRC-101 target in tumor cells, and ATRC-101 combined with doxorubicin enhanced efficacy compared with either agent alone. Taken together, these data demonstrate that ATRC-101 drives tumor destruction in preclinical models by targeting a tumor-specific RNP complex leading to activation of innate and adaptive immune responses.

GM-CSF disruption in CART cells modulates T cell activation and enhances CART cell anti-tumor activity.

Inhibitory myeloid cells and their cytokines play critical roles in limiting chimeric antigen receptor T (CART) cell therapy by contributing to the development of toxicities and resistance following infusion. We have previously shown that neutralization of granulocyte-macrophage colony-stimulating factor (GM-CSF) prevents these toxicities and enhances CART cell functions by inhibiting myeloid cell activation. In this report, we study the direct impact of GM-CSF disruption during the production of CD19-directed CART cells on their effector functions, independent of GM-CSF modulation of myeloid cells. In this study, we show that antigen-specific activation of GM-CSFKO CART19 cells consistently displayed reduced early activation, enhanced proliferation, and improved anti-tumor activity in a xenograft model for relapsed B cell malignancies. Activated CART19 cells significantly upregulate GM-CSF receptors. However, the interaction between GM-CSF and its upregulated receptors on CART cells was not the predominant mechanism of this activation phenotype. GM-CSFKO CART19 cell had reduced BH3 interacting-domain death agonist (Bid), suggesting an interaction between GM-CSF and intrinsic apoptosis pathways. In conclusion, our study demonstrates that CRISPR/Cas9-mediated GM-CSF knockout in CART cells directly ameliorates CART cell early activation and enhances anti-tumor activity in preclinical models.

154TiP AdvanTIG-204: Anti-TIGIT monoclonal antibody (mAb) ociperlimab (OCI) plus anti-PD-1 mAb tislelizumab (TIS) plus concurrent chemoradiotherapy (cCRT) in patients (pts) with untreated limited-stage small cell lung cancer (LS-SCLC)

Pts with LS-SCLC have a modest prognosis (5-year survival rate: 25–30%) and require more effective therapies. T-cell immunoreceptor with immunoglobulin and tyrosine-based inhibitory motif domains (TIGIT) is a co-inhibitory immune checkpoint receptor upregulated on T-cells and natural killer cells in multiple solid tumors, which can inhibit anticancer immune responses. Dual targeting of tumors with anti-TIGIT and anti-programmed cell death protein 1 (PD-1) produces synergistic immune cell activation and enhanced antitumor activity in preclinical models. OCI is a humanized, mAb that binds TIGIT with high specificity and affinity, blocking interaction with its ligands on tumor cells. TIS is an anti-PD-1 mAb engineered to minimize binding to Fc-gamma receptors on macrophages to abrogate antibody-dependent phagocytosis, a potential resistance mechanism to anti-PD-1 therapy. AdvanTIG-204 is a phase 2, randomized, multicenter, open-label study (NCT04952597). Approximately 120 treatment-naïve pts with LS-SCLC will be randomized 1:1:1 to receive either OCI 900 mg intravenously (IV) + TIS 200 mg IV combined with cCRT for 4 cycles, followed by OCI 900 mg + TIS 200 mg (Arm A), TIS 200 mg IV combined with cCRT for 4 cycles, followed by TIS 200 mg IV (Arm B), or cCRT only for 4 cycles (Arm C). OCI and TIS will be administered once every 3 weeks for ≤ 12 months, or until disease progression, unacceptable toxicity, death or withdrawal of consent, whichever occurs first. RT start early within Cycle 1 or 2 of systemic therapy. Pts will be stratified by disease stage (I/II vs III). The primary endpoint is PFS as assessed by the investigator (RECIST v1.1) in the intent-to-treat population. Secondary endpoints include, complete response rate, overall response rate, duration of response, overall survival (all investigator-assessed), correlation of PD-L1 and TIGIT expression with efficacy endpoints, and safety. Exploratory endpoints include, but are not limited to, biomarker evaluation, health-related quality of life, and circulating tumor DNA. Study enrollment is ongoing. NCT04952597. Medical writing support for the development of this abstract, under the direction of the authors, was provided by Tamsin Grewal, MSc, of Ashfield MedComms, an Ashfield Health company, and was funded by BeiGene, Ltd. BeiGene, Ltd.

DS-7300a, a DNA Topoisomerase I Inhibitor, DXd-Based Antibody-Drug Conjugate Targeting B7-H3, Exerts Potent Antitumor Activities in Preclinical Models.

B7-H3 is overexpressed in various solid tumors and has been considered as an attractive target for cancer therapy. Here, we report the development of DS-7300a, a novel B7-H3-targeting antibody-drug conjugate with a potent DNA topoisomerase I inhibitor, and its in vitro profile, pharmacokinetic profiles, safety profiles, and in vivo antitumor activities in nonclinical species. The target specificity and species cross-reactivity of DS-7300a were assessed. Its pharmacologic activities were evaluated in several human cancer cell lines in vitro and xenograft mouse models, including patient-derived xenograft (PDX) mouse models in vivo. Pharmacokinetics was investigated in cynomolgus monkeys. Safety profiles in rats and cynomolgus monkeys were also assessed. DS-7300a specifically bound to B7-H3 and inhibited the growth of B7-H3-expressing cancer cells, but not that of B7-H3-negative cancer cells, in vitro. Additionally, treatment with DS-7300a and DXd induced phosphorylated checkpoint kinase 1, a DNA damage marker, and cleaved PARP, an apoptosis marker, in cancer cells. Moreover, DS-7300a demonstrated potent in vivo antitumor activities in high-B7-H3 tumor xenograft models, including various tumor types of high-B7-H3 PDX models. Furthermore, DS-7300a was stable in circulation with acceptable pharmacokinetic profiles in monkeys, and well tolerated in rats and monkeys. DS-7300a exerted potent antitumor activities against B7-H3-expressing tumors in in vitro and in vivo models, including PDX mouse models, and showed acceptable pharmacokinetic and safety profiles in nonclinical species. Therefore, DS-7300a may be effective in treating patients with B7-H3-expressing solid tumors in a clinical setting.

A phase 3 randomized, double-blind, placebo-controlled, multicenter, global study of durvalumab with and after chemoradiotherapy in patients with locally advanced, unresectable esophageal squamous cell carcinoma: KUNLUN.

TPS373 Background: Esophageal cancer is the eighth most common cancer type and the sixth leading cause of cancer-related death worldwide, and esophageal squamous cell carcinoma (ESCC) is the most common type of esophageal cancer. For patients with locally advanced, unresectable ESCC (AJCC 8th Stage II–IVA), definitive chemoradiotherapy (dCRT) is the current standard of care; however, up to half of patients will experience disease progression within two years of dCRT, and overall survival rates remain suboptimal. The combination of immune checkpoint inhibitors with CRT has demonstrated synergistic antitumor activity in pre-clinical models, and recent clinical data has demonstrated clinical benefit of combined programmed cell death-1 inhibition and preoperative CRT in patients with locally advanced ESCC. KUNLUN (NCT04550260) is a Phase 3, multicenter, global study evaluating the efficacy and safety of durvalumab, a programmed cell death ligand-1 (PD-L1) inhibitor, given concurrently with, and after, dCRT in patients with locally advanced, unresectable ESCC. Methods: Approximately 600 patients will be randomized 2:1 to receive either durvalumab with dCRT (cisplatin plus fluorouracil or cisplatin plus capecitabine, with a total dose of 50–64 Gy radiation), followed by durvalumab for up to approximately 24 months, or placebo with dCRT, followed by placebo for up to approximately 24 months. Eligible patients will have histologically or cytologically confirmed ESCC, and present with locally advanced, unresectable ESCC that is deemed suitable for dCRT. Patients must have an Eastern Cooperative Oncology Group performance status of 0 or 1, and have not received prior anti-cancer treatment. The co-primary endpoint of the study is progression-free survival according to RECIST v1.1 as assessed by blinded independent central review in all randomized patients and in patients with PD-L1-high tumors. Additional endpoints include overall survival and safety. Study enrollment is ongoing. Funding: This study was sponsored by AstraZeneca.