By Elizabeth Dilts, Benjamin Lesser, Carl O'Donnell and Michael Erman. : NEW YORK (Reuters) - Last August, National Securities Corp analyst Jonathan Aschoff was bullish on Avenue Therapeutics Inc (ATXI.O), a fledgling biotechnology company with no revenue and one drug in clinical trials. In a research note posted on National’s website, he rated the newly listed stock a “buy” and predicted that the share price would more than double in a year. A few months earlier, Aschoff had waxed equally optimistic about another biotech venture, Checkpoint Therapeutics Inc (CKPT.O), with several cancer drugs in various stages of development.