CHICAGO >> Doctors are reporting big gains against melanoma, the deadliest form of skin cancer. Two studies on novel drugs find they can extend survival dramatically.

An experimental drug, vemurafenib (vem-yoo-RAF’-eh-nib), helped so much that people getting a comparison drug were allowed to switch after just a few months. It targets a gene mutation found in half of all melanomas and is being developed by Roche’s Genentech unit and Plexxikon Inc., part of Daiichi Sankyo.

The second study tested Bristol-Myers Squibb Co.’s Yervoy (YER’-voy), a just-approved treatment for newly diagnosed melanoma patients. It nearly doubled the number who survived at least three years.

Results were reported Sunday at a cancer conference in Chicago.