On December 6, 2021 Merus N.V. (Nasdaq: MRUS) ("Merus", "the Company", "we", or "our"), a clinical-stage oncology company developing innovative, full-length multispecific antibodies (Biclonics and Triclonics), reported that clinical data on MCLA-145 from the phase 1 trial in patients with solid tumors at the ESMO (Free ESMO Whitepaper) Immuno-Oncology Congress 2021 being held virtually (Press release, Merus, DEC 6, 2021, View Source [SID1234596496]).

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"We are encouraged by the progress we are making with MCLA-145," said Dr. Andrew Joe, Chief Medical Officer. "Patients have been treated at 8 dose levels with preliminary evidence of antitumor activity observed, as we continue to explore MCLA-145 as monotherapy."

MCLA-145

The reported data are from the phase 1 open-label, multicenter dose escalation study, of bispecific antibody MCLA-145 in patients with solid tumors. The primary objective is to evaluate the safety, tolerability, and dose-limiting toxicity (DLT) of MCLA-145 and to determine maximum tolerated dose (MTD) and/or recommended dose for expansion (RDE).

Observations in the presentation include:

As of the data cutoff date of July 14, 2021, 34 patients with advanced or metastatic solid tumors with median age of 60.5 (range 27-81) years have been treated at 8 dose levels ranging from 0.4-75mg Q2W
Median (range) duration of treatment with MCLA 145 was approximately 6 (1–74) weeks
Reported adverse events (AEs) have been managed with drug interruption and/or administration of steroids in some patients
Treatment-emergent AEs (TEAEs) occurred in 33 patients (97.1%); treatment-related TEAEs occurred in 23 patients (67.6%), most commonly fatigue (n=6, 17.6%) and decreased neutrophil count (n=6, 17.6%)
DLTs defined as within 28 days from the first infusion occurred in 4 patients (11.8%)
Laboratory alanine transaminase/aspartate transaminase (ALT/AST) elevations of any grade were observed in 15 patients (44.1%), with grade ≥3 ALT/AST elevations in 6 patients (17.6%)
Preliminary evidence of antitumor activity has been observed at doses ≥25 mg biweekly
Peripheral blood shows robust T-cell activation, including activation of cytotoxic CD8+ cells and cytokines, across the 10 to 75 mg biweekly dosing range
Further evaluation of optimal dose and efficacy in PD-L1+ tumors is planned.
The phase 1 clinical trial of MCLA-145 consists of a dose escalation phase, followed by a planned dose expansion phase. MCLA-145 is the first drug candidate co-developed under Merus’ global collaboration and license agreement with Incyte, which permits the development and commercialization of up to 11 bispecific and monospecific antibodies from the Merus Biclonics platform. Merus retains full rights to develop and commercialize MCLA-145, if approved, in the United States; and Incyte holds full rights to develop and commercialize MCLA-145 outside the United States.