HealthCor, a New York investment firm that owns 15 percent of Morrisville drug company Trimeris, wants the company to strongly consider a sale.In a letter to the company’s board of directors, HealthCor’s two chief executives run down a litany of complaints about Trimeris and its HIV drug, Fuzeon - most notably that the company’s stock is undervalued and that management’s plan to turn things around won’t work.