PALO ALTO, Calif. (AP) -- Drug developer Affymax Inc. said Tuesday it has appointed board member Hollings Renton as chairman, effective Dec. 1.

Renton will replace Nick Galakatos, who will resign from the board at the end of the year to focus on biopharmaceutical startups at venture capital firm Clarus Ventures.

Renton has been on the Affymax board since June. He was previously CEO and chairman of Onyx Pharmaceuticals Inc., chief operating officer of Chiron Corp. and chief financial officer of Cetus Corp., which was bought by Chiron.

Shares of Affymax, based in Palo Alto, Calif., fell 34 cents to $20.51 in late morning trading.