Drug Stock Crushed By Short Seller Report

ARNA and MRNS stocks are trading sharply higher today

The Dow is set for a nice win today, thanks in part to rising oil prices. Three stocks making notable moves are drugmakers Arena Pharmaceuticals, Inc. (NASDAQ:ARNA), Marinus Pharmaceuticals Inc (NASDAQ:MRNS), and Proteostasis Therapeutics Inc (NASDAQ:PTI). Let's take a closer look at what's moving shares of ARNA, MRNS, and PTI.

Trial Results Drive ARNA Near Top of Nasdaq

ARNA stock is trading up 30% at $40.20 -- one of the top Nasdaq gainers today -- after the company released positive mid-stage trial data for its chronic bowel disease drug. This news prompted price-target hikes from Cantor Fitzgerald ($64) and Leerink ($63). Looking back, Arena Pharmaceuticals had been in an impressive uptrend until a sharp sell-off last week, with the shares earlier topping out just below their March 5 two-year high of $44.50. The security certainly has the backing of Wall Street, with five of the six covering analysts handing out "strong buy" recommendations.

Mizuho Gives Struggling MRNS a Bump

A fresh "buy" rating and $13 price target at Mizuho has shares of MRNS up 10.6% at $4.52. The stock needed the bounce, as it'd been trending lower since its December peak near $10. It earlier broke above the 20-day moving average for the first time since early February -- though it's already moved back below this level. At the same time, Marinus was trading near just $1.50 this time last year.

Meanwhile, some short sellers have been exiting positions. Specifically, short interest fell by 17.8% over the last two reporting periods.

Kerrisdale Capital Goes Short On PTI Stock

Proteostasis Therapeutics has dropped 22.5% to trade at $5.42, after the company announced a public stock offering of 9 million shares. Plus, Kerrisdale Capital said it's shorting PTI, adding the drugmaker's cystic fibrosis treatment isn't as impressive as it appears, while calling for downside of 70%-90%. This puts PTI shares back below their year-to-date breakeven of $5.83, though they remain well above their 52-week low of $1.41. The equity may have been due for a pullback regardless, given its 14-day Relative Strength Index (RSI) of 81 at yesterday's close -- deep in overbought territory.