Let's take a quick look at four stocks which could make waves in the biotech sector this morning: MannKind (MNKD -1.68%), Mallinckrodt (MNK), Questcor (NASDAQ: QCOR), and Novartis (NVS 0.80%).

MannKind plunges after a three month extension of its PDUFA date
MannKind has fallen more than 10% in pre-market trading this morning, after the FDA extended its review of Afrezza to July 15. Afrezza, which could be the second market approved inhalable insulin after Pfizer's (NYSE: PFE) discontinued Exubera, was originally scheduled for a Prescription Drug User Fee Act (PDUFA) decision on April 15. However, numerous analysts had already anticipated the delay, due to lingering concerns about Afrezza's safety and efficacy.

The future looked bright for MannKind last week, after an FDA advisory panel voted to recommend the market approval of Afrezza for glycemic control in type 1 and 2 diabetes. The advisory panel voted 13 to 1 in favor of the type 1 indication and 14 to 0 in favor of the type 2 indication. Shares of MannKind nearly doubled after that announcement. Now, instead of waiting until April 15 for a final decision, MannKind investors will have to wait three more months.

Afrezza uses a faster-acting mealtime insulin analog compared to Exubera's slower-acting human insulin, and also requires a much smaller inhaler. However, it's still unclear if MannKind can convince diabetics to switch over from injected insulin analogs such as Novo Nordisk's Novolog.

MannKind, which finished last quarter with only $70.8 million in cash and equivalents, also needs a larger pharmaceutical partner to help market Afrezza.

Mallinckrodt buys Questcor for $5.6 billion
Meanwhile, Mallinckrodt agreed to buy Questcor Pharmaceuticals for $5.6 billion in cash and stock this morning to add its pipeline of autoimmune and inflammatory diseases to its portfolio. That price, which values Questcor at $86.08 per share, represents a 27% premium over Questcor's closing price on April 4.

Shares of Questcor are up 27% in pre-market trading this morning, while shares of Mallinckrodt are up 4%. Questcor's only approved product is the H.P. Acthar Gel, which is approved for 19 uses including infantile spasms, multiple sclerosis, rheumatic disorders, and dermatologic disease. Sales of the product rose 50% year-over-year last year to $761.3 million.

This is Mallinckrodt's second acquisition this year, after it agreed to purchase Cadence Pharmaceuticals for $1.3 billion in February. The acquisition of Cadence, which added an intravenous form of acetaminophen known as Ofirmev to Mallinckrodt's portfolio, was made for a 26% share price premium at $14 per share.

Mallinckrodt was spun off of medical device and pharmaceuticals giant Covidien last year. The company develops, manufactures, and markets branded and generic pharmaceuticals, active pharmaceutical ingredients (APIs), and diagnostic imaging agents.

Last quarter, Mallinckrodt's non-GAAP adjusted earnings rose 35% year-over-year to $0.88 per share while its revenue climbed 7.2% to $540.2 million, fueled by strong sales of its specialty pharmaceuticals.

The FDA grants Novartis' Bexsero a breakthrough designation
Last but not least, Novartis just announced that its meningitis B vaccine Bexsero received a breakthrough therapy designation from the FDA. Bexsero is already approved in Europe, Canada, and Australia, and is currently the only broad coverage meningitis B vaccine which can be administered to infants starting at two months of age.

Although Bexsero hasn't been approved by the FDA, Novartis provided nearly 30,000 doses of the vaccine to Princeton University and the University of California Santa Barbara after meningitis B outbreaks under an IND (investigational new drug) designation from the FDA.

Bexsero is one of Novartis' 12 key marketed vaccines, and one of three of its meningococcal vacccines, along with Menjugate (Meningococcal C vaccine for children older than 2 months) and Menveo (Meningococcal A,C, W-135, and Y vaccine for people between 2 months and 55 years of age).

Novartis' Vaccines and Diagnostics segment generated sales of $2 billion in fiscal 2013. After divesting its blood transfusion diagnostics unit to Grifols in January, the division only consists of vaccines. The division is notably the only one of Novartis' five business segments to report an operating loss in 2013.