Shares of Janux Therapeutics surged after its prostate cancer treatment was selected for expansion trials following what it called encouraging efficacy and safety results.

The stock jumped 71%, to $68.9, in over-night trading. Shares, which ended the regular session down 11%, to $40.18, have surged 274% since the beginning of the year.

The biopharmaceutical company's prostate cancer treatment, called JANX007, resulted in high prostate-specific antigen response rates and deep prostate-specific antigen declines across all doses in a Phase 1a clinical trial.

Based on these results, the drug will undergo expansion trials directed at pre-Pluvicto 2L and 3L patients. These are patients that haven't used Pluvicto, an existing therapy that delivers radiation directly to prostate-specific membrane antigen-positive cancer cells, and are on second-line and third-line treatment regimens, respectively.

"We look forward to rapidly advancing JANX007 into second- and third-line therapy where a substantial unmet need remains and where we believe JANX007's highly differentiated profile could allow for broad usage, if approved," Chief Executive David Campbell said.