Mirati Therapeutics Inc. started a $75 million underwritten public offering of its common shares.

The San Diego-based biotechnology company will give underwriters an option to buy up to an additional $11.3 million in shares.

J.P. Morgan Securities LLC, Citigroup Global Markets Inc., Cowen and Co. LLC, Barclays Capital Inc. and Credit Suisse Securities (USA) LLC are offering's joint book-running managers.

Mirati Therapeutics develops drugs that target genetic changes in cancer cells which cause tumors to grow and spread.