The chair of G1 Therapeutics Inc., a Durham-based biopharmaceutical company, sold 10,000 of the company’s shares for a net gain of $493,310, according to a filing with the Securities and Exchange Commission.

Seth Rudnick acquired 10,000 shares of G1 stock at an option price of 39 cents a share, a purchase of $3,900. Rudnick then sold the shares at an average price of $49.82 for a total of $497,210 and a net gain of $493,310.

Rudnick has sold 10,000 shares of G1 stock every month for the past three months.

On Aug. 6, Rudnick acquired and sold 10,000 shares at $50.69 a share for a net gain of $503,000.

Rudnick again acquired and sold 10,000 shares on Sept. 6 at an average price of $60.12 per share, resulting in a net gain of $595,583.

The three transactions have netted Rudnick $1.6 million since August.

As of Friday, when the transaction took place, G1’s stock was down 89 cents, closing at $44.69 — a 1.95 percent drop.

G1 Therapeutics is a biopharmaceutical company focused on the development and sale of innovative technologies related to cancer treatment. It is developing two inhibitors — trilaciclib and lerociclib — that are in clinical trials.

Rudnick has over 30 years of experience in the biotechnology and pharmaceutical industries and has served as chair of G1 since 2014. For 16 years, he was a partner at venture capital firm, Canaan Partners, where he oversaw investments in biopharmaceutical and medical devices.