Lately, the stock market has turned on every word from the Federal Reserve, and so this morning's comments from Federal Reserve Chairwoman Janet Yellen received a huge amount of attention from investors Monday. With Yellen offering a much more encouraging assessment of how long interest rates might remain low in order to stimulate and sustain economic growth, stocks climbed sharply, with the Dow posting triple-digit gains. Yet for MannKind (NASDAQ:MNKD), Momenta Pharmaceuticals (NASDAQ:MNTA), and Idera Pharmaceuticals (NASDAQ:IDRA), the news today was far from good, as all three stocks suffered declines of 10% or more.

MannKind plunged 17% as investors grow pessimistic about the chance that its Afrezza inhaled insulin product will gain FDA approval. An FDA advisory panel released materials related to Afrezza late last week, and the voluminous disclosure has analysts mixed on the likelihood of eventual FDA approval based on the materials. With Afrezza marking the only major prospect for MannKind, the company needs to have the drug approved for at least one type of diabetes in order to avoid what could become a catastrophic drop for MannKind stock.

Source: Wikimedia Commons.

Momenta also dropped 17%, as rival Teva Pharmaceutical (NYSE:TEVA) got good news from the Supreme Court in its battle to protect its Copaxone drug for multiple sclerosis. Momenta is ready to launch a generic version of Copaxone with partner Novartis (NYSE:NOV), and an initial decision would have allowed Momenta to start those sales by May. After choosing not to add the case to its calendar on two separate occasions, the Supreme Court's decision will have a major impact on Momenta's plans. With a possible Supreme Court decision pending, Teva has at the very least bought some time and could eventually wrest victory from Momenta for a much longer period.

Idera stock fell 10% today, giving back much of its 18% gains from Friday. Friday's jump came after the biotech company announced favorable data in a phase 2 trial of a treatment for plaque psoriasis, with its IMO-8400 giving strong indications of safety and efficacy. Yet investors likely reined in their enthusiasm, as some analysts expressed concerns about not getting to see more information on dosing effects and other key elements of the trial. With Idera having gotten hit hard earlier this month due in part to the market's sudden hatred of all things biotech, the company needs to work harder to give investors everything they want to see from all of its trial results.