Shares of Alexion Pharmaceuticals Inc. (ALXN) rose 6.7% to $139.88 in premarket trading on Thursday, July 27, after the New Haven, Conn.-based firm unveiled second-quarter results.

Alexion reported Non-GAAP earnings per share of $1.56, up 38% from the same period last year. Revenue was $912 million, representing a 21% year-over-year rise. Analysts had forecast, on average, adjusted EPS of $1.26 on revenue of $846.59 million, according to Bloomberg.

"In [our] view, this result, and the associated upward revision to guidance, was the most important of the large cap group this quarter," wrote Geoffrey C. Porges, of Leerink Partners in a note Thursday. The result, "was also the most uncertain, and we expect the stock to be up sharply on the news, thus rewarding investors for their patience and persistence over the last 9 months."

The company also raised revenue guidance to $3.45 billion to $3.525 billion, compared with the previous range of $3.40 billion to $3.50 billion, and increased non-GAAP EPS guidance to $5.40 to $5.55, from $5.10 to $5.30. Alexion narrowed its GAAP EPS guidance to $2.82 to $3.12, from $2.80 to $3.20.

Meanwhile, shares of United Therapeutics Corp. (UTHR) were up 5% to $138. The firm reported second-quarter non-GAAP earnings per diluted share of $4.37, down 1% from the same period a year ago. Revenue rose 8% to $444.6 million, which marks the company's highest quarterly net revenue level ever, chairman and CEO Martine Rothblatt noted in the news release.

Analysts had projected adjusted EPS of $3.79 on revenue of $391.50 million.

Among the other biotech stock movers was Gilead Sciences Inc. (GILD) , up 2.4% to $76. The Foster City, Calif.-based firm on Wednesday reported second-quarter non-GAAP diluted EPS of $2.56 per share, compared with $3.08 in the year-ago period. Total revenue was $7.1 billion, compared with $7.8 billion a year ago.

Analysts had forecast adjusted EPS of $2.14 on revenue of $6.34 billion.

Gilead also updated its full-year 2017 guidance. It now expects net product sales to be in the $24 billion to $25.5 billion range, compared with prior guidance of $22.5 billion to $24.5 billion.

"Q2 results were better than expected and good against low expectations and guidance raised (consistent w/ our EPS preview) but in part helped by US inventory shifts and EU 1x accounting adjustment," wrote Jefferies analyst Michael Yee in a Wednesday note.

Meanwhile, AstraZeneca plc's (AZN) U.S.-listed shares were down 15% to $28.73 apiece after disappointing trial results for a pipeline lung cancer drug were released. The trial, called Mystic, was a key component of the company's successful defense against Pfizer Inc's (PFE) hostile £69.4 billion ($91.2 billion) bid of 2014 and its failure renewed deal chatter around AstraZeneca.

Worried about how to finance your golden years? Register here to watch a free webinar in which TheStreet's Jim Cramer talks with Ken Fisher, founder of Fisher Investments, about the market trends shaping retirement planning today.

More of What's Trending on TheStreet:

More from Health

How to Become a Physician Assistant: What to Know

How to Become a Physician Assistant: What to Know

What is THC? Experts Weigh in on the Compound's Benefits and Effects

What is THC? Experts Weigh in on the Compound's Benefits and Effects

How Much Does a Physician Assistant Make?

How Much Does a Physician Assistant Make?

Buy These 3 Risky Biotech Stocks

Buy These 3 Risky Biotech Stocks

Successfully Plan for Retirement With a Triple-Tax-Free Health Savings Account

Successfully Plan for Retirement With a Triple-Tax-Free Health Savings Account