Opko Health Inc. (NASDAQ:OPK) is one of the best stocks under $3 to invest in. On February 4, Opko Health Inc. (NASDAQ:OPK) announced it expanded its partnership with Entera Bio Ltd., a company developing oral peptide and protein replacement therapies, to advance the first oral long-acting PTH analog (LA-PTH) treatment for patients with hypoparathyroidism, in the form of a once-daily tablet. The two companies have also jointly decided to accelerate development on this medication and expect to file an Inves ...