Paluri, Ravi Kumar

Abstract Background: T-cell immunoreceptor with immunoglobulin and immunoreceptor tyrosine-based inhibitory motif domain (TIGIT) is an inhibitory immune checkpoint receptor expressed on subsets of T-cells and natural killer (NK) cells. TIGIT inhibits T and NK cell function by binding to CD155 and CD112. SEA-TGT is an investigational human, nonfucosylated monoclonal antibody directed against TIGIT, blocking TIGIT's interaction with CD155 and CD112. SGNTGT-001 (NCT04254107) is a phase 1, open-label, multicenter study of SEA-TGT in patients (pts) with advanced malignancies (solid tumors and lymphomas). In this abstract, we present data from the dose-escalation phase (Part A). Methods: Pts received SEA-TGT ranging from 0.01 to 6.0 mg/kg of body weight intravenously every 3 weeks (Q3W). The primary objectives were to evaluate the safety and tolerability of SEA-TGT and identify the maximum tolerated dose (MTD) or the recommended dose and schedule of SEA-TGT. The optimal biological dose was defined using the Clinical Utility Index. Secondary objectives included the evaluation of antitumor activity, pharmacokinetics (PK) and immunogenicity. Antitumor activity was based on Response Evaluation Criteria in Solid Tumors version 1.1 or the Lugano classification criteria with Lymphoma Response to Immunomodulatory Therapy Criteria. Results: From June 12, 2020, to October 5, 2022, 41 pts were enrolled (2, 4, 5, 11, 12, and 7 pts in the 0.01, 0.1, 0.3, 1, 3, and 6 mg/kg cohorts, respectively). Among the 39 pts who were treated 23 pts had solid tumors and 16 had lymphomas. The median number of prior therapies across all cohorts was 5. Treatment emergent adverse events of any grade were reported in 100% of pts, and treatment-related adverse events (TRAEs) of any grade were reported in 69.2%. TRAEs seen in ≥10% of the pts were infusion-related reaction (38.5%), chills (25.6%), pyrexia (17.9%), fatigue (12.8%), maculopapular rash (12.8%), and rash (10.3%). Seven pts (17.9%) reported TRAEs grade ≥3, and rash (5.1%) was the most frequently reported. No grade 4 or 5 TRAEs were reported. One dose-limiting toxicity, pruritic rash, was observed in 1 pt in the 6 mg/kg cohort, and MTD was not exceeded. Based on the PK and pharmacodynamic data, 1 mg/kg Q3W was selected as the optimal biological dose for the expansion cohorts. One partial response was observed in a pt with gastric cancer, and 2 partial metabolic responses were seen in a pt with Hodgkin’s lymphoma and a pt with diffuse large B-cell lymphoma. Conclusions: Overall, clinical data for SEA-TGT from the SGNTGT-001 trial suggest a manageable and tolerable safety profile. Preliminary antitumor activity warrants further clinical evaluation of SEA-TGT. SGNTGT-001 is ongoing and evaluating monotherapy and combination therapies. Citation Format: Elena Garralda Cabanas, Elisa Fontana, Honey Kumar Oberoi, Nataliya V. Uboha, Ecaterina E. Dumbrava, Emiliano Calvo, Giuseppe Curigliano, Diwakar Davar, Bridget K. Keenan, Vincent K. Lam, Sudhir Manda, Amitkuma Mehta, Anna Minchom, Alison Moskowitz, Ravi Paluri, Vincent Ribrag, Donald Richards, Lillian Siu, Paul Swiecicki, Trisha Wise-Draper, Jasmine Zain, Andres Forero-Torres, Ping Xu, Stephen Ansell. Phase 1 dose-escalation study of SGN-TGT monotherapy in patients with advanced malignancies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT265.

Abstract Esophageal cancer is the sixth leading cause of cancer-related deaths worldwide. Squamous cell carcinoma is the most common histology in Eastern Europe and Asia, and adenocarcinoma is most common in North America and Western Europe. Surgery is a major component of treatment of locally advanced resectable esophageal and esophagogastric junction (EGJ) cancer, and randomized trials have shown that the addition of preoperative chemoradiation or perioperative chemotherapy to surgery significantly improves survival. Targeted therapies including trastuzumab, ramucirumab, and pembrolizumab have produced encouraging results in the treatment of patients with advanced or metastatic disease. Multidisciplinary team management is essential for all patients with esophageal and EGJ cancers. This selection from the NCCN Guidelines for Esophageal and Esophagogastric Junction Cancers focuses on recommendations for the management of locally advanced and metastatic adenocarcinoma of the esophagus and EGJ.

268 Background: TRC105, an endoglin antibody, potentiates the activity of sorafenib (S) in preclinical HCC models, and TRC105 + S demonstrated a 33% partial response rate (5/15 pts) by RECIST, at RP2D doses of TRC105 in HCC pts ( Clin Can Res 2017). Adverse events characteristic of each drug were not increased in frequency or severity when the two drugs were administered concurrently. Methods: P1: Compare wkly TRC105 dosing vs four wkly doses followed by every other wkly dosing + S 800 mg daily. P2: Four objective responses are required in 21 pts to reject the null hypothesis that the true response rate probability is < 5% with an alpha level of 0.1 and 80% power. Key inclusion criteria: disease not amendable to surgical or local therapies, ECOG ≤ 1; Child-Pugh A or B (7 points) classification. Results: Thirteen pts were enrolled in phase 1b at TRC105 10 mg/kg wkly for four doses and 15 mg/kg every other week thereafter + S. Mean serum levels of TRC105 exceeded the target conc. following 4 wkly doses of TRC105 at 10 mg/kg (mean = 34 µg/ml, range BLOQ-80). Mean trough conc. decreased following every other week dosing (mean = 13 µg/ml, range BLOQ-31), resulting in infusion reactions or a continued requirement for premedication. Therefore, wkly dosing of TRC105 at 10 mg/kg is the recommended Phase 2 dose. ADA were detected in 10 of 14 pts and correlated with lower than expected PK conc. Common TRC105 related AEs included ≤ G2 epistaxis, ≤ G2 fatigue and ≤ G2 headache. Common S related AEs included ≤ G3 fatigue, ≤ G3 hand foot syndrome and ≤G2 epistaxis. A total of 3 out of 14 evaluable patients (21%) enrolled in phase 1 and 2 achieved durable PR, 2 of these ongoing at week 45 and 17. Conclusions: TRC105 dosed at 10 mg/kg wkly was required to achieve target conc. due to higher clearance in HCC pts, which may have been influenced by a higher rate of ADA compared to studies of TRC105 in other tumor types. The combination of TRC105 + S demonstrated encouraging signs of activity, including durable PR in 2/9 evaluable pts in Phase 1b and 1/5 pts thus far in Phase 2. An additional 16 pts will be enrolled at the RP2D to assess the primary endpoint of ORR by RECIST. Clinical trial information: NCT01806064.

301 Background: Endoglin plays a critical role in angiogenesis and is implicated in resistance to VEGF inhibition. TRC105, an endoglin antibody potentiates anti-tumor activity of sorafenib (S) in preclinical HCC models. The combination of TRC105 and S demonstrated encouraging evidence of activity, including a 33% partial response rate (5/15 pts) by RECIST, at RP2D doses of TRC105 in HCC ( Clin Can Res 2017). Adverse events characteristic of each drug were not increased in frequency or severity when the two drugs were administered concurrently, and most commonly included epistaxis, fatigue, headache and anemia. Methods: Following dose escalation, 21 pts will be enrolled at the RP2D. Four objective responses are required to reject the null hypothesis that the true response rate probability is < 5% with an alpha level of 0.1 and 80% power. Secondary endpoints: DR, PFS, frequency and severity of AEs, PK, immunogenicity, angiogenic biomarkers. Key inclusion criteria: disease not amendable to surgical or local therapies, ECOG ≤ 1; Child-Pugh A or B (7 points) classification. Results: Four pts have been enrolled in phase 1b at TRC105 10 mg/kg (n=4) weekly for four doses and 15 mg/kg every other week thereafter + S 800 mg daily without DLT. One of 3 evaluable pts achieved PR (41% reduction), ongoing at month 4. Serum levels of TRC105 exceeded the target concentration following 4 weekly doses of TRC105 at 10 mg/kg (mean = 59 µg/ml, range 43-80). Mean trough concentration decreased following every other week dosing (mean = 21 µg/ml, range 17-31). Common TRC105 related AEs included ≤ G2 epistaxis and G1 headache. Common S related AEs included G3 hand foot syndrome, ≤G3 periodontal disease, G2 hypertension, ≤G2 increased lipase, ≤G2 fatigue and G1 epistaxis. Conclusions: TRC105 dosed by a hybrid schedule of 10 mg/kg weekly for four doses followed by every other week dosing at 15 mg/kg was tolerable and did not potentiate the toxicity of S. The combination of TRC105 + S demonstrated additional signs of activity, including a PR in 1/3 evaluable pts. 21 pts will be enrolled at the RP2D to assess the primary endpoint of ORR by RECIST. Clinical trial information: NCT01806064.