Amgen Inc. has agreed to license an experimental pain drug to a subsidiary of Johnson & Johnson for an initial payment of $50 million and as much as $385 million in additional payments if the drug works as expected.

The agreement, announced late Thursday, gives Ortho-McNeil-Janssen Pharmaceuticals Inc., a division of New Brunswick, N.J.-based J & J;, the global rights to the drug except in Japan, Amgen said. The Thousand Oaks-based biotech company has a previous licensing arrangement for the drug in that country. The drug, which suppresses nerve growth, has not been given a name yet.

The deal is subject to approval by federal antitrust regulators.

Shares in Amgen were flat Friday morning at $62.80.