Merus N.V. announced updated interim clinical data on MCLA-145 monotherapy and in combination with pembrolizumab were presented at the 2024 American Society of Clinical Oncology®? (ASCO®) Annual Meeting taking place in Chicago May 31, 2024 to June 4, 2024. MCLA-145 (CD137 x PD-L1 Biclonics®): Solid Tumors: Interim data included in the presentation describe data from patients (pts) with advanced/metastatic solid tumors who received MCLA-145 Q2W in 28 day cycles or every three weeks (Q3W) in 21 day cycles.

Pts treated with the combination of MCLA-145 and pembrolizumab had cancers that either relapsed after PD-(L)1 therapies or were immunotherapy (IO) naïve. Rapid oral presentation title: Phase I study of MCLA-145, a bispecific antibody targeting CD137 and PD-L1, in solid tumors, as monotherapy or in combination with pembrolizumab Observations in the presentation include: As of a January 3, 2024 data cutoff date, 72 pts with multiple cancer types were treated; 25% of pts had non-small cell lung cancer (NSCLC); All patients were heavily pre-treated with a median of 3 prior therapies; prior IO in 49% of the monotherapy pts and 100% of the combination pts; In monotherapy, 52 pts with a variety of tumor types and treated at different dose levels were evaluable for response; 5 partial responses (PRs) were observed at different dose levels in glioblastoma (ongoing as of the cutoff date for >3 years), sarcoma (pretreated with pazopanib and gemcitabine/docetaxel), cervical, anal, and gastric cancer by Response Evaluation Criteria in Solid Tumors v1.1. per investigator assessment; 2 of 6 pts PRs (33%) were observed for pts treated at the recommended dose for expansion (RDE), 40 mg Q3W; 3 of 6 PRs (50%) were observed for pts with evaluable baseline tumor CD8 T-cell density of = 250 cells/mm2 responded; In combination with pembrolizumab, 19 pts with a variety of tumor types and treated at different dose levels were evaluable for response; 1 PR in Merkel cell carcinoma was observed at 25 mg Q3W; 1 complete response was observed in PD-L1+ NSCLC at the RDE 40 mg Q3W; 3 pts were continuing combination therapy at cutoff date; MCLA-145 monotherapy or in combination with pembrolizumab had a well-tolerated and manageable safety profile at the RDE, 40mg Q3W; Shifting from Q2W to Q3W resulted in a 50% reduction of Grade (G) =3 treatment-emergent adverse events in both monotherapy and combination therapy; Liver toxicity, a common CD137 related adverse event, was controlled with no G4 events observed at Q3W.