Benzinga | Dec 10, 2021 08:04AM EST

Merus Presents Updated Analysis Of Zenocutuzumab, Trastuzumab, And Vinorelbine In Patients With HER2+ Metastatic Breast Cancer At San Antonio Breast Cancer Symposium

Merus N.V. (NASDAQ:MRUS) ("Merus", "the Company", "we", or "our"), a clinical-stage oncology company developing innovative, full-length multispecific antibodies (Biclonics(r) and Triclonics(r)), presented clinical data on zenocutuzumab (Zeno) in combination with trastuzumab and vinorelbine in patients (pts) with HER2 positive/amplified (HER2+) metastatic breast cancer (MBC) who had progressed on anti-HER2 antibody drug conjugates (ADC), at the San Antonio Breast Cancer Symposium in San Antonio, Texas.

Andrew Joe, Chief Medical Officer at Merus, said, "We are pleased to present the final analysis of the triplet Zeno combination which has demonstrated clinically meaningful activity in heavily pretreated patients with HER2+/amplified MBC. We are encouraged by Zeno's potential to be active in indications outside NRG1 fusion cancers, opening opportunities for potential collaborations in these areas."

The reported data are from the completed phase 2 study, designed to explore the efficacy of a triplet combination of Zeno plus trastuzumab and vinorelbine in MBC patients (NCT03321981). Preliminary results for patients treated with the triplet regimen were presented at the American Society of Clinical Oncology 2020 Annual Meeting. The combination was observed to be well-tolerated in the run-in cohort and the cohort was expanded. The primary endpoint of the study was clinical benefit rate (CBR) at 24 weeks of 45%. Updated results from the cohort expansion are presented here:

* At the efficacy data cut-off, March 31, 2021, 39 patients, with a median age of 57 and with a median number of five prior therapies, had received the Zeno-based triplet combination, 4 of whom were ongoing. All patients had completed at least 6 months of treatment or discontinued

* 37 patients with locally confirmed HER2 overexpression (IHC 3+ or IHC 2+/FISH-positive) were evaluable for antitumor activity

* The clinical benefit rate (CBR: complete response + partial response + stable disease ?24 weeks) per investigator assessment was 49% (18/37 patients; 90% CI 34 - 63)

* Confirmed responses (per investigator) were reported in 10 patients, including 2 patients with complete response (CR)

* Median duration of response was 4.2 months (90% CI 2.8 - 12.4), including 2 patients with CR lasting 4.2 and 7.2+ months, and 8 patients with partial responses (PR) lasting from 2.6 to 12.4 months

* Median progression-free survival was 5.5 months (90% CI 4.1 - 5.6); 7 patients (19%) were censored. Estimated overall survival rates at 12 and 24 months were 73% and 61%, respectively

* The combination was observed to be well tolerated, with AEs primarily related to chemotherapy

As previously reported, with completion of this phase 2 trial, Merus does not have plans to advance into a phase 3 clinical trial in metastatic breast cancer in the absence of a partner. The company continues to focus on the eNRGy trial to potentially support a BLA submission seeking a tumor agnostic indication for Zeno in patients with previously treated NRG1+ cancers.

The full poster is available on our website.