Women’s cancers: new drug keeps advanced breast cancer in check longer

If you or someone you love is living with breast cancer, here is good news from the world of women’s cancers: there is a new treatment option for women whose cancer has outlasted several other medicines.

A drug called iza-bren kept this type of breast cancer from growing for much longer than standard chemotherapy did. The result comes from a large, well-designed trial, and it gives doctors and patients one more tool when choices have been running short.

How the study worked

Researchers at 72 hospitals in China enrolled 383 women with hormone receptor-positive, HER2-negative breast cancer. That is the type that feeds on hormones and does not carry extra HER2 protein. Every woman’s cancer had kept growing after hormone therapy, after a class of drugs called CDK4/6 inhibitors, and after one or two rounds of chemotherapy.

By chance, half were assigned to iza-bren and half to the chemotherapy their doctor would normally choose. Reviewers who did not know which treatment each woman received judged whether the cancer had grown. The trial was published on Oct. 26, 2026, in The Lancet. Patients and doctors knew which drug was used, all the women were of Chinese ethnicity, and data on how long women lived overall are still too early to read.

What is iza-bren?

Its full name is izalontamab brengitecan. It belongs to a group called antibody-drug conjugates.

Think of a guided missile. The antibody part finds cancer cells by locking onto two proteins on their surface, called EGFR and HER3. The drug part is a strong chemotherapy payload that it delivers right to those cells.

What they found

Women who received iza-bren went much longer before their cancer grew than women who received chemotherapy. The difference between the two groups was large enough that it is very unlikely to be down to chance.

The drug did come with more serious side effects. About 85% of women on iza-bren (162 of 190) had a serious treatment-related side effect, compared with about 66% on chemotherapy (127 of 193). In both groups, the most common problems were blood-related, such as low blood counts.

The care team handled those blood problems with support treatments:

The exact figures were 138 women (73%) for platelet-raising medicines, 28 (15%) for platelet transfusions and 18 (10%) for blood transfusions. Two women in the iza-bren group died from treatment-related side effects. This is why the drug is given with close monitoring.

What this means for you

When cancer has already outlasted several treatments, more time without growth is meaningful. This trial shows that a new kind of medicine can deliver it for women with this common type of breast cancer. The authors say iza-bren could become a new treatment option, and they call for testing in other populations and in earlier stages of treatment.

What you can do today

If you or someone close to you has this type of breast cancer and it has grown after several treatments, write one question for the next oncology visit: “Are antibody-drug conjugates or a clinical trial an option for me now?” You can also bring a list of the treatments tried so far. ClinicalTrials.gov, the national registry where this study is listed under NCT06343948, is a place to start looking for trials near you.