5 A Phase 1b, Open-Label, Safety, Tolerability, and Efficacy Study of HC-7366 in Combination with Belzutifan (WELIREGTM) in Patients with Advanced or Metastatic Renal Cell Carcinoma, NCT06234605

Abstract Background HC-7366 is a novel, orally administered, highly selective and potent activator of general control nonderepressible 2 (GCN2) kinase, a core regulator of metabolic stress through activation of the integrated stress response (ISR). Activation of GCN2 promotes cell survival, whereas prolonged activation induces apoptosis. GCN2 activation also suppresses general protein synthesis and induces cell cycle arrest, thereby preventing cell growth during nutrient scarcity. Additionally, HC-7366 decreases HIF expression and inhibits glycolysis, oxidative phosphorylation, and TCA cycle function. HC-7366 also inhibits HIF expression in immunosuppressive myeloid cells, including macrophages. These effects of HC-7366 on metabolism, HIF signaling, and immune suppression suggest therapeutic benefit in ccRCC with clear rationale for combinations with HIF2a antagonists and immune checkpoint inhibitors. HC-7366 (0.5-1 mg/kg), combined with belzutifan (1 mg/kg), exhibited combination benefit in HIF-2 dependent A-498 and 786-O RCC xenografts, yielding 90% tumor growth inhibition and a three-fold increase in complete responses, respectively. Additionally, HC-7366 drives significant monotherapy antitumor activity in PDX models that demonstrated belzutifan resistance. Mechanism of action studies have identified several pathway engagement and potential efficacy biomarkers (Stokes, et al., 2024). Trial design/schema This multicenter, open-label phase 1b study will identify the Maximum Tolerated Dose (MTD) and/or the Recommended Phase 2 Dose (RP2D) of HC-7366 in combination with fixed-dose belzutifan, 120 mg po qd, in patients with advanced or metastatic RCC with renal cell histology irrespective of VHL gene mutation. Monotherapy HC-7366 will be evaluated in parallel. The monotherapy arm, HC-7366, 60 mg p.o. qd, includes patients who have relapsed after 1 to 4 prior lines of standard of care that may include belzutifan or another HIF-2α inhibitor. The combination arm includes patients who have received 1 to 3 prior lines of standard of care and are belzutifan or HIF-2α naïve. HC-7366 dose escalation arm evaluates combination fixed dose belzutifan, 120 mg po qd plus HC-7366 at 20, 40, or 60 mg po qd. Enrollment will start with the HC-7366 monotherapy arm. Subsequently, patients will begin to enroll in the combination therapy HC-7366 dose escalation arm, while the monotherapy arm will continue to enroll. Expansion will evaluate the combination of fixed dose belzutifan with two doses of HC-7366 selected from escalation. Assessments include safety, PK, and anti-tumor activity. The study will enroll up to 80 patients at US study sites. Significance and vision Combination HC-7366 plus belzutifan, supported by preclinical evidence, is being studied to assess antitumor activity in the RCC relapsed setting. Determining safety and evaluation of dose are foundational to this study. Reference Stokes M, Tameire F, Wojnarowicz P, et al. HC-7366, a potent GCN2 activator, complements belzutifan, a HIF-2⍺ antagonist, by providing combination benefit in belzutifan-sensitive models and monotherapy activity in belzutifan-resistant models. Meeting of the American Association for Cancer Research; 2024 Apr 5-10; San Diego (CA); AACR; 2024. Abstract 4615. This study is in collaboration with Merck Sharp & Dohme LLC, a subsidiary of Merck & Co., Inc., Rahway, NJ, USA