Analyst Update: Twitter Inc, Vertex Pharmaceuticals Incorporated, and Inovio Pharmaceuticals Inc

Analysts are weighing in on social media stock Twitter Inc (NYSE:TWTR), as well as biotechs Vertex Pharmaceuticals Incorporated (NASDAQ:VRTX) and Inovio Pharmaceuticals Inc (NASDAQ:INO). Here's a quick roundup of today's brokerage notes on TWTR, VRTX, and INO.

• It's been a volatile day so far for TWTR, following a note from Morgan Stanley. The brokerage firm said it believes the social media company's third-quarter earnings -- due out on Thursday afternoon -- will show a decline in ad revenue, which will extend into the fourth quarter. Meanwhile, Axiom increased its third-quarter earnings outlook for TWTR, but maintained its "hold" recommendation, citing "rising competition for user time from Snapchat and Instagram, and pricing that is at a premium [to] other platforms."
  
  Although the stock dropped more than 3% earlier, it was last seen slightly higher at $18.15. Of course, Twitter Inc shares have been battered over the past 12 months, sliding 41%. Amid this fall, short sellers have been cashing in their winning bets. Since peaking in mid-May, short interest has declined 39.4%, and it would take less than one day to cover the remaining shorted shares, at the stock's average pace of trading.

• VRTX has shed 1.8% today to trade at $79.32, after H.C. Wainwright downgraded the stock to "neutral" from "buy" and dropped its price target to $85, saying the drugmaker may have missed the boat on dominating the cystic fibrosis market. The brokerage firm added, "We do not view this company as able to sustain a valuation far in excess of its current $20 bln in the near term." Today's drop is more of the same for a stock that's now down 37% since the start of the year, and additional losses could spark more downgrades. For example, Vertex Pharmaceuticals Incorporated sports 11 "buy" or "strong buy" ratings, while not a single brokerage firm recommends selling the shares. Looking ahead, the company will report third-quarter earnings after tomorrow's close. 

• INO is getting pummeled today, down 17% at $6.94 --- earning a spot on the short-sale restricted list -- after the Food and Drug Administration (FDA) put a clinical hold on the company's proposed late-stage trial for its cancer treatment, saying it needs more information to move forward. In response, Stifel dropped its price target on Inovio Pharmaceuticals Inc to $11 from $13, but maintained its "buy" opinion. The brokerage firm said, "Importantly, this clinical hold is not due to any dosing or safety concerns," and that the additional data requested by the FDA will be "straightforward to generate." Still, INO is on pace for its first close below its 320-day moving average since its late-March bull gap. This is just fine with short sellers, though, who control one-fifth of the stock's float.