Sumitomo Dainippon Pharma Oncology Announces Phase 3 CanStem303C Study of Napabucasin Fails to Reach Primary Endpoints in Patients with Previously Treated Metastatic Colorectal Cancer

As of April 1, 2022 Sumitomo Dainippon Pharma Oncology (SDP Oncology) will be known as Sumitomo Pharma Oncology (SMP Oncology). Moving forward, all new publications and press releases will reflect our updated company name.

CAMBRIDGE, Mass., Feb. 9, 2021 /PRNewswire/ -- Sumitomo Dainippon Pharma Oncology, Inc., a developer of novel cancer therapeutics, today announced that the CanStem303C study evaluating the efficacy and safety of investigational agent napabucasin when given in combination with FOLFIRI with or without bevacizumab in patients with previously treated metastatic colorectal cancer failed to reach the primary endpoints of overall survival (OS). Napabucasin in combination with FOLFIRI failed to show significant OS improvement in the general study population and in patients whose tumor was positive for the phosphorylated signal transducer and activator of transcription 3 (pSTAT3) biomarker.

"Patients with metastatic colorectal cancer have a high unmet medical need, and our hope was to develop a new treatment option for this population. We are disappointed with the results of this Phase 3 trial and would like to express gratitude to the trial participants, investigators and staff for their efforts and contributions to the study," said Patricia S. Andrews, CEO and Global Head of Oncology, Sumitomo Dainippon Pharma Oncology (SDP Oncology). "SDP Oncology is committed to continuing our pursuit of advancing our pipeline to bring forward innovative treatments for patients with cancer."

The multicenter, open-label, randomized Phase 3 CanStem303C study evaluated the efficacy and safety of napabucasin in approximately 1,250 patients with previously treated metastatic colorectal cancer. Patients were randomized 1:1 in the study. The study had two primary endpoints – overall survival in all randomized patients and overall survival in a subpopulation of patients whose tumor was positive for the pSTAT3 biomarker. Napabucasin at a dose of 240 mg was administered orally, twice daily in combination with FOLFIRI with or without bevacizumab versus FOLFIRI with or without bevacizumab.

The most common adverse events, occurring in patients in the napabucasin combination arm, were consistent with previously published data and included diarrhea, nausea, vomiting and abdominal pain.

Final data and analyses of this study will be published for the oncology community.

About Napabucasin

Napabucasin is an investigational, orally administered reactive oxygen species (ROS) generator that is bioactivated by the intracellular antioxidant NAD(P)H:quinone oxidoreductase 1 (NQO1).1 Napabucasin exerts its antitumor activity by increasing levels of ROS beyond a cytotoxic threshold, causing cancer cell death.1,2

About Colorectal Cancer

Colorectal cancer is the third leading cause of cancer-related deaths in men and in women in the U.S. It is estimated that there will be 149,500 new cases of colorectal cancer and 52,980 deaths from colorectal cancer in the U.S. this year.3 Metastatic colorectal cancer occurs when cancer cells break way from a tumor in the colon or the rectum to other parts of the body through the bloodstream or lymphatic system.4 Approximately 22% of colorectal cancer cases are metastatic at initial diagnosis, and about 70% of patients will eventually develop metastatic relapse. Patients with metastatic colorectal cancer face poor prognosis in general, with a relative 5-year survival rate of 14%, compared to 71% and 90% in those with regional and localized colorectal cancer in the U.S.5

About Sumitomo Dainippon Pharma Oncology

Sumitomo Dainippon Pharma Oncology, Inc., is a wholly owned subsidiary of Sumitomo Dainippon Pharma Co., Ltd. As a global oncology organization with teams in the U.S. and Japan, SDP Oncology is relentlessly committed to advancing purposeful science by transforming new discoveries into meaningful treatments for patients with cancer. The company's robust and diverse pipeline of preclinical and advanced-stage assets spans multiple areas, including oncogenic pathways, survival mechanisms and novel protein interactions, which aim to address unmet clinical needs in oncology.

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About Sumitomo Dainippon Pharma

Sumitomo Dainippon Pharma is among the top-10 listed pharmaceutical companies in Japan, operating globally in major pharmaceutical markets, including Japan, the U.S., China and the European Union. Sumitomo Dainippon Pharma aims to create innovative pharmaceutical products in the Psychiatry & Neurology area, the Oncology area and Regenerative medicine/Cell therapy field, which have been designated as the focus therapeutic areas. Sumitomo Dainippon Pharma is based on the merger in 2005 between Dainippon Pharmaceutical Co., Ltd., and Sumitomo Pharmaceuticals Co., Ltd. Today, Sumitomo Dainippon Pharma has more than 6,000 employees worldwide. Additional information about Sumitomo Dainippon Pharma is available through its corporate website at

Disclaimer Regarding Forward-Looking Statements

This press release contains "forward-looking statements," as that term is defined in the Private Securities Litigation Reform Act of 1995 regarding the research, development and commercialization of pharmaceutical products. The forward-looking statements in this press release are based on management's assumptions and beliefs in light of information presently available and involve both known and unknown risks and uncertainties. Any forward-looking statements set forth in this press release speak only as of the date of this press release. We do not undertake to update any of these forward-looking statements to reflect events or circumstances that occur after the date hereof. Information concerning pharmaceuticals (including compounds under development) contained within this material is not intended as advertising or medical advice.


1 Chang AY, Hsu E, Patel J, et al. Evaluation of tumor cell-tumor microenvironment component interactions as potential predictors of patient response to napabucasin. Mol Cancer Res. 2019;17(7):1429-1434.

2 Froeling F, Swamynathan MM, Deschênes A, et al. Bioactivation of napabucasin triggers reactive oxygen species-mediated cancer cell death. Clin Cancer Res. 2019;25(23):7162-7174.

3 American Cancer Society. Cancer Facts & Figures 2021. Atlanta, Ga: American Cancer Society; 2021.

4 Cancer Treatment Centers of America. Metastatic Colorectal Cancer Updated September 18, 2020. Accessed January 25, 2021.

5 Wang J, Li S, Liu Y, Zhang C, Li H, Lai B. Metastatic patterns and survival outcomes in patients with stage IV colon cancer: A population-based analysis. Cancer Med. 2020;9(1):361-373.

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