MIAMI (AP) — Noven Pharmaceuticals Inc. said Tuesday it is being bought by Japan-based Hisamitsu Pharmaceutical Co. for about $428 million in cash. The tender offer of $16.50 per share marks a 22.4 percent premium to Noven’s closing price of $13.48 Monday. In premarket trading Tuesday, the value climbed 22 percent to $16.50. Noven makes a range of transdermal patch-based treatments for attention deficit hyperactivity disorder and hormone therapy. Noven said it expects to remain a subsidiary of Hisamitsu after the buyout closes, while continuing to operating out of its current locations in Miami and New York with the existing work force. The buyout agreement was unanimously approved by the boards of directors of both Noven and Hisamitsu and a tender offer is expected to start July 28 and last for about 20 business days. J.P. Morgan Securities Inc. served as financial advisor to Noven in connection with the transaction, and Cravath, Swaine & Moore LLP served as Noven’s legal counsel.