Washington-based Vanda Pharmaceuticals Inc. has faced a challenging few years involving a federal lawsuit against the U.S. FDA, patent infringement litigation, increasing generic competition and dwindling sales, as well as a complete response letter nixing plans to expand its melatonin receptor agonist Hetlioz (tasimelteon) into insomnia, yet it has recently received a higher, unsolicited acquisition offer of $466 million from a second company, Cycle Pharmaceuticals Ltd.