Marengo's Invikafusp Alfa Combination Shrinks Tumours in 71% of Metastatic Breast Cancer Patients

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Marengo Therapeutics reported interim results from its Phase 1b/2 STARt-002 trial on Monday, showing its experimental T-cell drug invikafusp alfa, combined with the antibody-drug conjugate sacituzumab govitecan, produced tumour shrinkage in most patients with metastatic breast cancer who could be assessed. The findings were presented in an oral session at the Society for Immunotherapy of Cancer's 2026 annual meeting.

As of an October 16 data cutoff, 48 patients had enrolled across two groups: metastatic triple-negative breast cancer and hormone-receptor-positive, HER2-negative disease. Among the 38 patients who could be assessed for efficacy, 27 saw their target tumours shrink, and disease control reached 74 percent overall and 83 percent among patients who had not previously received an antibody-drug conjugate. Confirmed complete responses appeared in both groups, including one in a patient with PD-L1-negative triple-negative disease that was still going after more than a year.

The response rates were 28 percent in the triple-negative group and 25 percent in the hormone-receptor-positive group, rising to 36 percent among triple-negative patients who had not had a prior antibody-drug conjugate. Half the patients had already received at least three earlier lines of treatment in the metastatic setting. Laboratory work from the trial showed the drug expanded the intended Vbeta6-positive T-cell population in all eight patients tested during the first treatment cycle, matching what Marengo had seen with the drug alone. The combination's safety profile was described as manageable, with no unexpected toxicities and no treatment-related deaths.

The figures come from Marengo's release of the SITC presentation, and the headline counts check against the detailed breakdowns. Twenty-seven of 38 patients had tumour shrinkage, 28 of 38 had disease control, and the two cohorts' response rates add up to the overall picture. The trial is registered as NCT06827613, and an independent report from OncLive, based on the same presentation by Dr. Steven Isakoff of Mass General, gives the same enrolment and efficacy numbers while adding safety detail, including that cytokine release syndrome occurred in about 85 percent of patients and was mostly mild or moderate. The study is single-arm and the numbers are interim, so they show activity rather than proof that the combination beats sacituzumab govitecan alone.

Triple-negative and hormone-receptor-positive metastatic breast cancers that have already been through several treatments leave patients with few options, and checkpoint drugs help only a minority of them. A combination that pairs an antibody-drug conjugate with a drug designed to switch on selected T cells could widen the reach of immunotherapy into tumours that usually ignore it. Marengo's chief executive said the results support developing invikafusp alfa as a backbone for further combinations, and the company pointed to earlier single-agent signals across eight tumour types as the reason to keep pushing the approach into broader groups of patients.