TP Therapeutics, a small San Diego pharmaceutical company, has raised nearly $18 million in an all-equity Series B financing round, according to a recent form filed with the Securities and Exchange Commission.

Although investors were not disclosed, the form indicates 26 total investors.

The company, which is working to solve the problem of drug-resistant cancers, will use the money to continue development of its lead programs, said Jeff Whitten, VP of clinical development.

TP Therapeutics was founded in 2013 by Jean Cui and her husband Y. Peter Li.

Cui is the lead inventor of top-selling Pfizer cancer drug, Xalkori — an achievement that earned her prestige (along with many awards and honors) in the scientific community. The popular medication trounced chemotherapy in a 2014 lung cancer trial and currently has annual sales of $438 million. Some analysts are predicting that Xalkori could reach blockbuster potential by 2020, raking in over $1 billion per year.

When Xalkori reached the market in 2011, Cui wasn’t satisfied with her contribution to the patients.

“I saw problems with Xalkori and other drugs available for this type of cancer, and I knew that someone needed to work on these problems so that we could provide better medicines for patients,” Cui said in an interview with the San Diego Business Journal last year. “That’s why I resigned from Big Pharma ― to start a company that could solve these problems.”

TP Therapeutics, therefore, is tackling drug-resistant cancers ― a problem that Pfizer and other oncology drugmakers know too well.

Last year, the company was in late-stage pre-clinical trials, and planned to file an Investigational New Drug application with the FDA in 2016.