Daiichi Sankyo’s novel cancer treatment, Datroway (datopotamab deruxtecan), has officially received approval from Japan's Ministry of Health, Labour and Welfare (MHLW) for the treatment of adult patients with hormone receptor (HR) positive, HER2 negative unresectable or recurrent breast cancer after prior chemotherapy. This approval marks a significant milestone in the fight against one of the most prevalent forms of breast cancer in Japan.

In 2022, the country reported approximately 92,000 cases of breast cancer, making it the most common cancer among women in the country. Of these, approximately 70% were diagnosed with HR positive, HER2 negative breast cancer, a subtype typically characterized by a HER2 score of IHC 0, IHC 1+, or IHC 2+/ISH-. Given the challenging prognosis of these patients after previous chemotherapy treatments, Datroway offers a promising new alternative.

Datroway is the first TROP-2 directed medicine approved in Japan for HR positive, HER2 negative breast cancer. It is also the second DXd antibody drug conjugate (ADC) to be approved in the country, based on Daiichi Sankyo’s cutting-edge DXd ADC technology. This approval was primarily based on the results of the TROPION-Breast01 phase 3 trial, which evaluated Datroway's efficacy in treating metastatic HR positive, HER2 negative breast cancer. The study showed that Datroway significantly reduced the risk of disease progression or death by 37% compared to chemotherapy (hazard ratio [HR]=0.63, 95% CI: 0.52-0.76; p<0.0001).

Patients treated with Datroway experienced a median progression-free survival (PFS) of 6.9 months, compared to just 4.9 months in those who received conventional chemotherapy. These results highlight the potential of Datroway to transform treatment options for this challenging patient population.

“This first global approval of Datroway provides patients in Japan with metastatic HR positive, HER2 negative breast cancer a new alternative to conventional chemotherapy, which is often associated with poor response rates,” said Wataru Takasaki, PhD, Senior Advisor at Daiichi Sankyo. “Datroway also is the second DXd antibody drug conjugate approved in Japan based on technology invented by Daiichi Sankyo, emphasizing our commitment to creating new, innovative standards of care for patients with cancer.”

However, the approval comes with a warning for interstitial lung disease (ILD), a known side effect associated with Datroway treatment. In the TROPION-Breast01 trial, adverse reactions occurred in 93.6% of the 360 patients who received Datroway, with the most common side effects including nausea (51.1%), stomatitis (50%), alopecia (36.4%), fatigue (23.6%), and dry eye (21.7%). Notably, 6.5% of Japanese patients treated with Datroway experienced ILD. Due to the risk of ILD, including fatal cases, Datroway should be used under close supervision, particularly by respiratory disease experts.

Patients are advised to undergo thorough monitoring, including periodic chest CT scans, oxygen saturation tests, and chest X-rays, especially if symptoms such as dyspnea, cough, or fever arise. If any abnormalities are detected, Datroway treatment should be discontinued, and appropriate medical measures, such as corticosteroid administration, should be considered.

Datroway is also undergoing regulatory review in multiple regions, including the EU, China, and the United States, with additional approvals anticipated in the near future.

This landmark approval offers new hope to patients battling HR positive, HER2 negative breast cancer in Japan, underscoring the importance of continuous innovation in cancer therapies.