Check out the companies making headlines after the bell on Wednesday:

Shares of CRISPR Therapeutics plunged 18.5 percent in extended trading. The biotechnology company disclosed that the FDA has placed a clinical hold on its drug application for a sickle cell disease stem cell therapy. The suspension will be in effect until CRISPR and Vertex Pharmaceuticals answer FDA questions about the drug application.

Vertex shares crept down 0.4 percent after the announcement.

Box stock tumbled 6.5 percent in the extended session, before recovering some of its losses. The cloud storage company reported first quarter financial results that surpassed analyst expectations on top and bottom lines. Box reported loss per share of 7 cents on revenue of $141 million. The street was expecting a loss of 8 cents on $140 million.

Box shares have gained 31 percent year-to-date.

Shares of Guess fell as much as 2 percent after the bell, before recovering some losses. The clothing brand and retailer reported a 23 cent loss per share in the first quarter, which fell in-line with analyst expectations. Guess surpassed Wall Street projections on revenue, reporting $521 million versus the $508 million expected. The fashion brand issued weaker than anticipated earnings outlook for the second quarter and full year outlook.

Cars.com stock jumped 8 percent, before losing some of its gains in after hours trading. The classified auto listings site announced it had hired J.P. Morgan to explore a possible sale.

PVH shares wobbled in extended trading and turned negative. The clothing company, which owns brands, like Tommy Hilfiger and Calvin Klein, beat analyst expectations on first quarter earnings and revenue and issued strong second quarter and full-year guidance. The apparel manufacturer has demonstrated stronger growth in international markets, like Europe and Asia, than in North America.

Shares of Symantec edged down nearly 1 percent in after hours trading. The cybersecurity company, which owns Norton products, announced it would delay filing its annual shareholder report, related to an internal accounting probe announced earlier in May. The company informed shareholders it did not think the probe would have a material impact on its past financial statements.

Source: Tech CNBC
After-hours buzz: CRSP, BOX & more