Pyxis Oncology announces preliminary PYX-201 data, collaboration with Merck

Pyxis Oncology (PYXS) announced preliminary data from the ongoing Phase 1 clinical dose escalation study evaluating PYX-201 in multiple types of solid tumors. PYX-201, the company’s lead clinical drug candidate, is a first-in-concept antibody-drug conjugate with a microtubule inhibitor payload that uniquely targets Extradomain-B Fibronectin, a non-cellular structural component within the tumor extracellular matrix. Significant clinical responses were observed in HNSCC. Among evaluable HNSCC patients treated at an identified dose range of PYX-201 from 3.6 – 5.4 mg/kg, a confirmed 50% objective response rate, or ORR, was observed, including one confirmed complete response, or CR, and two confirmed partial responses, or PR, by RECIST 1.1. The company additionally announces that it has entered into a clinical trial collaboration agreement with Merck (MRK) for a Pyxis Oncology-sponsored study of PYX-201 in combination with Merck’s anti-PD-1 therapy, Keytruda in patients with 1L and 2L head and neck squamous cell carcinoma, HR+/HER2- breast cancer, and triple-negative breast cancer and sarcoma. The company expects to initiate the following HNSCC Phase 1 expansion studies: PYX-201 and Keytruda combination dose escalation and expansion study in 1L and 2L HNSCC with preliminary clinical data readout expected in the second half of 2025; PYX-201 monotherapy study in 2L and 3L HNSCC patients who are platinum and PD-1 inhibitor experienced, with preliminary clinical data readout expected in the second half of 2025 and PYX-201 monotherapy study in 2L and 3L HNSCC patients who are EGFR and PD-1 inhibitor experienced, with preliminary clinical data readout expected in first half of 2026. Exploratory PYX-201 Phase 1 monotherapy expansion cohorts are planned in ovarian cancer, NSCLC, HR+/HER2- breast cancer, TNBC, and sarcoma, with preliminary clinical data expected in the second half of 2025. PYX-201 and Keytruda combination study in HR+/HER2- breast cancer, TNBC, and sarcoma with preliminary clinical data expected in the second half of 2025 and the first half of 2026. Preclinical studies of PYX-201 in combination with other agents in ovarian cancer and NSCLC to commence in 2025 to be followed by clinical studies with preliminary clinical data expected in 2026. PYX-201 demonstrated favorable preliminary tolerability profile data with low incidence of dose discontinuation, interruptions or delays due to treatment-related adverse events. Low incidence of Grade 3 or Grade 4 payload-related TRAEs within the identified dose range reinforce PYX-201’s differentiated construct enabling enhanced molecular stability and differential expression of Extradomain-B in tumor tissue with negligible expression in normal tissues. The low incidence of Grade 1 or Grade 2 adverse events points to an attractive safety, given that it has been well tolerated and suitable for both monotherapy and combination therapy development. With respect to PK data, PYX-201 demonstrated increased stability in circulation, which we believe is due to its proprietary design of site-specific conjugation chemistry as compared to certain approved val-cit-monomethyl auristatin E ADCs with non-site-specific conjugation chemistry.