Marengo's Immunotherapy Shows 'Complete Response' in Advanced Breast Cancer

CAMBRIDGE, Mass. – April 17, 2026 – In a series of announcements that have captured the attention of the oncology community, clinical-stage biotech firm Marengo Therapeutics has unveiled promising early results for a new combination therapy in metastatic breast cancer. The company reported that its novel T-cell activator, invikafusp alfa, when combined with Gilead Sciences' antibody-drug conjugate TRODELVY®, has produced confirmed complete responses in patients who had previously exhausted other treatment options.

The late-breaking data, presented at the 2026 American Association for Cancer Research (AACR) Annual Meeting, was complemented by the announcement of a second Marengo-developed therapy, IPN01203, advancing into clinical trials with partner Ipsen. The dual milestones signal significant momentum for Marengo's innovative approach to programming the immune system to fight cancer.

A New Strategy for a Challenging Disease

The most striking results come from the ongoing STARt-002 Phase 1b/2a trial, which is evaluating the invikafusp alfa and TRODELVY® combination. The study includes patients with metastatic triple-negative breast cancer (TNBC) and HR+/HER2- breast cancer, two subtypes that are notoriously difficult to treat, especially after multiple lines of therapy have failed.

For this “heavily pretreated” population, the observation of a “complete response”—meaning the disappearance of all signs of cancer—is a profound development. It suggests the combination therapy may be effective where others are not.

“Combining invikafusp alfa with ADC-mediated immunogenic tumor killing is a scientifically compelling approach, and it is exciting to see this translate into meaningful clinical responses in patients with metastatic breast cancer,” said Kevin Chin, M.D., Chief Medical Officer of Marengo Therapeutics. “The observation of confirmed complete responses in heavily pretreated breast cancer patients that did not respond to any prior therapy further reinforces our confidence in this novel combination.”

Crucially, the combination therapy has so far shown a safety profile consistent with the known effects of each individual drug, with no new safety concerns emerging. This is a critical factor in the development of any combination regimen. The STARt-002 trial continues to enroll patients, with completion expected later this year, which will provide a fuller picture of the therapy’s efficacy and safety.

Dr. Erika Hamilton, a noted breast cancer research leader, emphasized the importance of these early findings. “In a heavily pretreated metastatic breast cancer population, the observation of confirmed complete responses is notable and warrants attention,” she stated. “While these are early data, the activity observed across both TNBC and HR+/HER2− subtypes, along with a safety profile consistent with the individual agents, supports further clinical evaluation of this combination.”

'Hitting the Gas' on the Immune System

At the heart of Marengo’s progress is its proprietary Selective T Cell Activation Repertoire (STAR) platform. This technology represents a departure from first-generation immunotherapies like checkpoint inhibitors, which work by “taking the brakes off” the immune system. Marengo’s approach is more akin to “hitting the gas” on specific, targeted groups of T cells.

Invikafusp alfa, the company's lead candidate, is an antibody-fusion molecule that selectively activates a common subset of T cells (Vβ6/Vβ10) found in all individuals. It does this by binding to the T cell receptor (TCR) and providing a co-stimulatory signal simultaneously, effectively supercharging these immune cells.

The strategy of combining this T-cell agonist with an antibody-drug conjugate (ADC) like TRODELVY® is particularly innovative. TRODELVY® works by delivering a potent chemotherapy agent directly to cancer cells that express the Trop-2 protein. This targeted killing of cancer cells causes them to release tumor antigens, creating a more “immunologically hot” environment. The activated T cells, supercharged by invikafusp alfa, can then more easily recognize and attack these newly exposed cancer targets, creating a powerful, synergistic anti-tumor effect and potentially establishing long-term immune memory.

Validated by High-Profile Partnerships

Beyond the promising clinical data, Marengo's dual announcements at AACR underscore a successful business strategy built on high-value collaborations. The STARt-002 trial is conducted in partnership with Gilead Sciences, which supplies TRODELVY® for the study.

Even more significant is the company's deep collaboration with the global biopharmaceutical company Ipsen. In 2022, Ipsen paid Marengo $45 million upfront, with the potential for over $1.5 billion in future milestone payments, to develop two candidates from the STAR platform. The first of these, now known as IPN01203, has officially advanced into a Phase 1/2 clinical trial sponsored by Ipsen, a milestone highlighted in the prestigious “New Drugs on the Horizon” session at AACR.

“Together with Marengo, we are advancing a novel precision T cell activation approach with the potential to transform treatment paradigms in solid tumors,” said David Jenkins, Senior Vice President at Ipsen. “The rapid progression of this program into the clinic underscores the strength of our collaboration and the quality of scientific execution.”

Marengo’s CEO, Zhen Su, M.D., MBA, echoed this sentiment, stating, “This milestone reflects both the strength of our platform and the productivity of our collaboration as we work together to bring novel immunotherapies to patients with solid tumors.”

This partnership not only provides significant financial backing but also serves as a powerful external validation of Marengo's underlying technology from a major pharmaceutical player. It gives Marengo access to Ipsen's global development and commercialization infrastructure, accelerating the path to market for its next wave of therapies.

With its lead program delivering remarkable early signals in a high-need area and its platform technology spawning a new clinical-stage asset with a major partner, Marengo Therapeutics has firmly established itself as a key innovator to watch in the next generation of cancer immunotherapy. As enrollment for the pivotal breast cancer study nears completion, the oncology community will be watching closely to see if this novel T-cell activation strategy can redefine treatment for some of the most challenging solid tumors.