AstraZeneca-Daiichi Sankyo breast cancer drug shows promise

British drugmaker AstraZeneca and Japan’s Daiichi Sankyo said on Wednesday their experimental treatment for breast cancer met its key goal in a mid-stage study, bolstering their position in a highly competitive oncology market.

The treatment trastuzumab deruxtecan, or DS-8201, demonstrated a clinically meaningful response in patients with stage 4 breast cancer and have a type of protein on the surface of cancer cells, the two companies said in a joint statement.

The positive results from the study underscore AstraZeneca’s bet on cancer medicines and specifically DS-8201. The British firm in March agreed to pay up to $6.9 billion to Daiichi on the hotly tipped treatment, in a direct challenge to the world’s biggest cancer drug maker Roche and cater to a condition that doesn’t have many successful treatments.

Trastuzumab deruxtecan was evaluated in patients with refractory HER2-positive metastatic breast cancer and were previously treated with another medicine trastuzumab emtansine, AstraZeneca and Daiichi said.

DS-8201 targets the HER2 protein, a major trigger of uncontrolled cell growth in about 20 percent of breast cancers, where Roche has been a pioneer with its ageing best-seller Herceptin.

AstraZeneca and Daiichi’s treatment is part of a drug class called antibody-drug conjugates (ADC), which links powerful cell toxins to antibodies that cling to cancer cells, sparing the healthy cells that are damaged during conventional chemotherapy treatments.