Phase 1 Open-Label, Multicenter Study of First-in-Class RORγ Agonist LYC-55716 (Cintirorgon): Safety, Tolerability, and Preliminary Evidence of Antitumor Activity

Purpose: Transcription factor retinoic acid receptor–related orphan receptor γ (RORγ) regulates type 17 effector T-cell differentiation and function and is key to immune cell regulation. Synthetic RORγ agonists modulate immune cell gene expression to increase effector T-cell activity and decrease immune suppression. A phase 1 study evaluated the safety and tolerability of LYC-55716 (cintirorgon), a first-in-class, oral, small-molecule RORγ agonist in adults with relapsed/refractory metastatic cancer. Patients and Methods: Patients received 28-day treatment cycles of oral LYC-55716; dose and dosing regimen were determined according to pharmacokinetic profile and safety. Primary endpoints were safety and tolerability. Secondary endpoints included pharmacokinetics and objective tumor response rate. Results: No dose-limiting toxicities occurred among the 32 enrolled patients who received LYC-55716 150 mg BID to 450 mg BID. Treatment-related adverse events (AE) were primarily grade 1–2 and included diarrhea (n = 11), fatigue (n = 7), anemia (n = 4), decreased appetite (n = 4), and nausea (n = 4). Grade 3 AEs were anemia (n = 2), elevated gamma-glutamyl transferase (n = 1), and hypophosphatemia (n = 1). Pharmacokinetic concentrations achieved levels expected for target gene regulation. Pharmacodynamic results indicated RORγ pathway engagement. Two patients (NSCLC and sarcomatoid breast cancer) had confirmed partial responses; 11 had disease stabilization for 2 to 12 months (6 received >4 months of treatment). Conclusions: These data support the safety and tolerability of LYC-55716 and selection of 450 mg BID dose for a phase 2a study assessing LYC-55716 clinical activity, safety, and biomarkers in patients with NSCLC, head and neck, gastroesophageal, renal cell, urothelial, and ovarian cancers.