On October 12, 2022 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 the publication of the abstract highlighting interim data from the ongoing phase 1/2 trial of the bispecific antibody MCLA-129 on the 34th EORTC/NCI/AACR Symposium on Molecular Targets and Cancer Therapeutics (ENA Symposium) website (Press release, Merus, OCT 12, 2022, View Source [SID1234621958]). MCLA-129 is a fully human IgG1 Biclonics bispecific antibody that binds to EGFR and c-MET and is being investigated in patients with advanced non-small cell lung cancer (NSCLC) and other solid tumors. This phase 1/2 study has completed the dose escalation phase and is on-going in the dose expansion phase.

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The poster will be presented at the 34th ENA Symposium in Barcelona, Spain on Friday, October 28, 2022, 10:00-15:00 CET, and will be available online Wednesday, October 26, 2022. The poster presentation will include additional interim clinical data from this dose escalation cohort.

"We are encouraged by the promising initial clinical data for MCLA-129 presented in the abstract and are looking forward to providing additional clinical data from the dose escalation cohort in the poster presentation at the ENA Symposium," said Dr. Andrew Joe, Chief Medical Officer at Merus. "We also intend to share a MCLA-129 program update on our upcoming conference call."

The reported interim data in the abstract are from the phase 1/2 trial of MCLA-129 in patients with advanced NSCLC and other solid tumors.

Information and observations in the abstract include:

As of the May 8, 2022 cutoff date, 20 patients were treated with MCLA-129 across doses of 100, 300, 600, 1000, and 1500 mg every two weeks
Median age of patients was 65 years (range 43-79)
Tumor types enrolled included:
14 patients with EGFR mutant (mt) NSCLC (4 L858R, 8 Del19, 1 exon 20 insertion, 1 other)
2 patients with c-MET exon 14 mt NSCLC
1 patient with c-MET amplified gastric adenocarcinoma
1 patient with squamous cell esophageal cancer
2 patients with head and neck squamous cell carcinoma
13 patients were evaluable for response with preliminary signs of anti-tumor activity observed:
Two partial responses (one confirmed) in EGFR mt NSCLC
Four confirmed stable disease
Median duration of treatment was 8 weeks (range 3.4- 29.3) with 11 patients still on treatment at the cutoff date
Safety:
No dose limiting toxicity was observed and maximum tolerated dose was not reached
The most frequently reported adverse event (AE) was infusion related reaction (IRR)
18 of 20 pts (90%) reported IRR after first dose, all but one were mild or moderate (grade 1-2)
All but one infusion were completed on the same day
No treatment discontinuations due to AE
No interstitial lung disease was observed
Recommended initial phase 2 dose for expansion is 1500 mg every two weeks. The expansion cohorts are enrolling.
Dose-dependent depletion of soluble EGFR and c-MET was observed
In doses ranging from 600-1500 mg every two weeks, MCLA-129 demonstrated linear pharmacokinetics
Mean serum concentrations at 1500 mg every two weeks dose are modeled to be above that required for >95% target engagement of cell-bound EGFR and c-MET throughout the dosing period
Presentation Details:

Title: MCLA-129, a human anti-EGFR and anti-c-MET bispecific antibody, in patients with advanced NSCLC and other solid tumors: an ongoing phase 1/2 study
First author: Prof. Sai-Hong Ignatius Ou, Department of Medicine, Division of Hematology Oncology, University of California Irvine School of Medicine, US
Session: New Therapies in Immuno Oncology
Date: Friday, October 28, 2022
Time: 10:00-15:00 CET
Abstract #: 341
Poster #: PB121

The poster will be available at the start of the conference on October 26, 2022 and on-demand throughout the conference on the conference website. The poster will also be available on the Merus website contemporaneously.

Company Conference Call and Webcast Information

Merus will hold a conference call and webcast for investors on Wednesday, October 26, 2022 at 13:30 CET/7:30am ET to discuss the MCLA-129 initial clinical data and provide a program update. A replay will be available after the completion of the call in the Investors and Media section of our website for a limited time.

About MCLA-129
MCLA-129 is an antibody-dependent cellular cytotoxicity-enhanced Biclonics that is designed to inhibit the EGFR and c-MET signaling pathways in solid tumors. Preclinical data have shown that MCLA-129 can effectively treat TKI-resistant non-small cell lung cancer (NSCLC) in xenograft models of cancer. MCLA-129 is designed to have two complementary mechanisms of action: blocking growth and survival pathways to stop tumor expansion and recruitment and enhancement of immune effector cells to eliminate the tumor.