Why Biogen, Groupon, and Omeros Slumped Today

Wednesday was another strong day for the stock market, with the Dow climbing more than 250 points after having opened the session in the red. Investors had initially feared the return of inflationary pressure after this morning's CPI report from the Labor Department, but despite higher bond yields, market participants ended up paying little attention to the implications and instead bid up stock indexes. For some companies, ignoring bad news wasn't quite as simple. Biogen (NASDAQ: BIIB), Groupon (NASDAQ: GRPN), and Omeros (NASDAQ: OMER) were among the worst performers on the day. Below, we'll look more closely at these stocks to tell you why they did so poorly.

Biogen makes investors nervous

Shares of Biogen dropped nearly 7%, with the fall coming fairly late in the day after the biotech company held a discussion at an industry conference about a clinical trial of its Alzheimer's candidate treatment. Biogen spoke at Leerink Partners' 7th Annual Global Healthcare Conference, saying that because of what it called increased variability in a study of its aducanumab treatment, Biogen will add 510 more Alzheimer's patients to the clinical trial. Bullish investors hope that the addition will make any conclusions about the study's primary endpoints clearer, but some fear that greater dispersion of benefits might in itself be a risk factor going forward.

Groupon disappoints with quarterly results

Groupon stock fell 9.5% after the company announced its fourth-quarter financial results early Wednesday. The e-commerce company best known for its once-groundbreaking daily deals business said that gross billings fell 2%, fueling a 4% drop in revenue and resulting in adjusted earnings that didn't live up to expectations. Groupon did say that active customers were on the rise, approaching nearly 50 million worldwide, and CEO Rich Williams touted an improved customer experience. Yet investors wanted more positive momentum after a strong 2017, and that helped send shares downward.

Omeros gets panned

Finally, shares of Omeros plunged nearly 18%. The small biotechnology company was the subject of a negative report from short-side research specialist FourWorld Capital Management, which set a $4 per share price on the stock. Followers of the company are concerned that the federal government didn't explicitly extend favorable Medicare reimbursement provisions for its cataract surgery product Omidria, and the move could threaten to hurt revenue going forward. After nearly doubling in 2017, Omeros' stock will need Omidria to be a hit in order to sustain recent gains.

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Dan Caplinger has no position in any of the stocks mentioned. The Motley Fool recommends Biogen. The Motley Fool has a disclosure policy.