A drug marketed by partners AstraZeneca and Daiichi Sankyo for certain breast, gastric, and lung cancers now has new clinical trial data suggesting the therapy could be used to treat more cancers regardless of where they are found in the body.

The drug, Enhertu, addresses tumors that express a cancer protein called HER2. This protein is found in many different tumor types, yet many cancers do not have FDA-approved HER2-targeting therapies. Across several patient cohorts representing a wide range of tumor types, treatment with the drug in a Phase 2 study led to an objective response rate of 37.1% across all study participants. The median duration of response to the treatment was 11.8 months. The results were presented Monday during the annual meeting of the American Society of Clinical Oncology.

Enhertu is an antibody drug conjugate (ADC), a type of therapy that links a toxic cancer-killing drug payload to an antibody that goes after a target on a tumor. The drug won its initial approval for treating HER2-positive breast cancers in 2019, followed by a 2021 regulatory nod in gastric cancer. At last year’s ASCO meeting, the drug was a big newsmaker with data showing it could also address breast cancer that expresses low levels of the protein. Last summer, Enhertu won approvals for treating such “HER2-low” breast cancers. FDA approval in non-small cell lung cancer followed soon after.

Though Enhertu’s first approval was in breast cancer, initial research with the drug also found anti-tumor activity in tumors of the salivary gland, biliary gland and endometrial cancers, said Funda Meric-Bernstam, chair of the department of investigational cancer therapeutics at University of Texas MD Anderson Cancer Center, speaking during a briefing with journalists. Meric-Bernstam is the principal investigator for the Phase 2 study that is assessing the drug’s ability to treat other HER2-expressing tumors.

AstraZeneca designed and sponsored the open-label Phase 2 clinical trial, which enrolled 267 patients spanning the following cancers: cervical, endometrial, ovarian, biliary tract cancer, pancreatic, and bladder. A seventh group enrolled rare tumor types excluding those represented by the other cohorts as well as breast, gastric, colorectal, and non-small cell lung cancers.

The 57.5% objective response rate in the endometrial cancer cohort was the highest of all the groups, but Meric-Bernstam noted that objective responses were also high in several other groups. The one exception was pancreatic cancer, which showed an objective response rate of 4%. In the Phase 2 results so far, there were no new safety signals reported for Enhertu.

“The trial is still ongoing, and we’ll be reporting overall survival and [progression-free survival] at a later date,” Meric-Bernstam said. “However, the data to date suggest that [Enhertu] has broad activity and could present a new therapy option for patients who are HER2 positive or expressive.”

Bradley McGregor, director of the Lank Center for Genitourinary Oncology at the Dana-Farber Cancer Institute, said the expression of HER2 by a wide range of tumors represents an unmet need for treating cancers. Aside from the results in the pancreatic cancer cohort, he said the interim Enhertu data reported at the ASCO meeting are encouraging.

“While early, I think this is really exciting and represents a shift in how we think about cancer care,” McGregor said.

Photo: Christopher Furlong, Getty Images