RG7741 (also known as GDC-0575) is an investigational small molecule designed to prevent tumor cells from recovering from DNA damage caused by chemotherapy.

It is being developed by Genentech, a subsidiary of Roche, as part of an oncology agreement with Array BioPharma.

How RG7741 works

RG7741 is a selective inhibitor of checkpoint kinase 1 (ChK1), an enzyme that regulates tumor cells’ response to DNA damage caused by chemotherapy. When DNA is damaged, ChK1 blocks cell growth to allow for damaged DNA to be repaired; in cancer, this limits the effectiveness of chemotherapy agents.

RG7741 specifically binds to and blocks Chk1. Inhibiting ChK-1 in combination with chemotherapy may enhance tumor cell death because it prevents tumor cells from recovering from damage that is intentionally directed at them. In other words, RG7741 is designed to make chemotherapy more effective.

RG7741 in clinical trials

Preclinical studies demonstrated that RG7741 inhibited cell growth in human cancer cell lines grown in the laboratory. They also showed that RG7741 halted the growth of tumor tissues in vivo, meaning outside a living organism (in the lab).

A two-part Phase 1 study (NCT01564251) is evaluating the safety, tolerability, and pharmacokinetics (the way a drug moves in the body) of RG7741 when administered alone or in combination with the chemotherapy drug Gemzar (gemcitabine) in people with drug-resistant solid tumors or lymphoma.

Patients in part one of the trial, which opened in 2012, are being given ascending oral doses of RG7741 alone or in combination with Gemzar to determine the maximum tolerated dose. In part two, they will receive RG7741 in combination with Gemzar at or below the maximum tolerated dose determined. Treatment will go on for up to five years until disease progression or unacceptable toxicity.

Primary objectives include safety, tolerability, and pharmacokinetics by measuring the number of adverse events, the number of participants with dose-limiting toxicities, the maximum tolerated dose, the recommended Phase 2 dose, and RG7741 blood concentrations at different moments in the study. Secondary goals include the duration of treatment response and progression-free survival.

The study enrolled 104 participants in the U.S. and France, and is estimated to conclude in June 2018.


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