A new class of ovarian and breast cancer drugs that thwart a DNA repair mechanism ushered in a novel approach to treating cancer. The first PARP inhibitor was approved in 2014. That drug, and others that followed, block a PARP enzyme that plays a key role in this repair process. But it turns out there’s more than one type of PARP—17, to be exact. Ribon Therapeutics aims to target other PARPs with small molecule drugs, and the Boston-area startup has raised $65 million in financing to bring its drugs into clinical trials, which could start later this year.
This Series B round was led by Novartis Venture Fund and other new investors Johnson & Johnson Innovation – JJDC, Inc. and Celgene (NASDAQ: CELG).
PARP enzymes all help the cell survive under stress, but they do this in different ways and in response to different kinds of stress. The PARP inhibitors now on the market, including olaparib (Lynparza), the market leader from AstraZeneca (NYSE:AZN), and niraparib (Zejula) from Tesaro, which was recently acquired by GlaxoSmithKline (NYSE:GSK), inhibit two members of the PARP family, PARP1 and PARP2. These enzymes help cells fix damaged DNA.
But Ribon is focused on a different set of PARP enzymes called monoPARPs, which Ribon says are linked to cancer and other diseases. Cancer cells, with their genetic mutations and relentless growth, are constantly under stress. With its drugs, Ribon aims to disable monoPARPs so that cancer cells are overwhelmed by the stress and die.
Ribon’s lead program is an inhibitor of PARP7. Ribon says certain cellular stresses, such as cigarette smoke, activate this enzyme, which then helps cancer cells survive and also allows them to dodge the immune system. The startup has a compound that blocks PARP7 that it’s developing initially for squamous cell lung cancer, a type of lung cancer often associated with smoking and, according to the company, is marked by high levels of PARP7. Victoria Richon, Ribon’s CEO, says her startup should begin clinical trials with this compound this year.
Richon adds that based on the preclinical data of the PARP7 inhibitor, her company aims to test it as a single anti-cancer agent, but is also exploring its use in combination with other cancer drugs.
With the new funding, Richon says her 26-employee company will move other development programs closer to the clinic, and is also evaluating whether its library of drug candidates could target other kinds of enzymes, and work in other diseases such as inflammatory and neurodegenerative disorders.
In addition to the new investors, Ribon’s earlier investors also participated in the Series B round: The Column Group, Deerfield Management, U.S. Venture Partners, Osage University Partners, Takeda Ventures and Euclidean Capital. See here for more on Ribon.