Let's take a look at four stocks -- MannKind (MNKD -0.36%), Dicerna Pharmaceuticals (DRNA), Flamel Technologies (FLML), and Merck (MRK 2.03%) -- which could all loom large in biotech headlines this Monday morning.

All eyes on MannKind following the FDA approval of Afrezza
MannKind is up more than 11% in pre-market trading this morning, in response to the FDA approval of Afrezza, its inhalable insulin for type 1 and type 2 diabetes, last Friday.

Afrezza was approved earlier than expected, but a boxed warning for patients with respiratory issues dampened optimism. Following Afrezza's approval on Friday afternoon, the stock initially soared nearly 5%, then fell, before finishing the day down nearly 6% as investors digested the news.

Despite its boxed warnings, analysts believe that Afrezza could generate peak annual sales of $600 million. Afrezza has several key advantages over Pfizer's ill-fated inhalable insulin Exubera, including a smaller inhaler, a faster acting insulin analog compared to Exubera's human insulin, and easy-to-remember linear doses compared to Exubera's confusing non-linear dosage pattern.

Afrezza's future hinges on three main things -- comparisons to insulin analogs like Novo Nordisk's Novolog, its final price (Exubera was more expensive than injected insulin), and marketing partner (what sort of deal, and if one occurs). I think MannKind needs a major partner to launch Afrezza, since the company finished last quarter with only $36 million in cash but $174 million in debt.

Dicerna soars on promising data for DCR-PH1
Shares of Dicerna Pharmaceuticals are up more than 5% in pre-market trading, after the company announced the presentation of clinical data demonstrating the promise of DCR-PH1, its experimental treatment for primary hyperoxaluria type 1 (PH1), a rare inherited liver disorder which results in progressive kidney damage. The research was presented at the 11th International Primary Hyperoxaluria Workshop in Chicago.

Preclinical studies showed that DCR-PH1 provided long-term inhibition of HAO1, a gene implicated in the progression of PH1, in a mouse model. Researchers noted a 97% reduction of the HAO transcript in the liver and a significant decline in urinary oxalate levels, a key benchmark for PH1. Keep in mind, this was a preclinical trial, so it's hard to assign any real value to the drug until we have at least some data from human trials, but the initial data appear positive.

Dicerna specializes in RNA-interfering drugs. Its pipeline consists of five treatments, one of which has reached phase 1 trials. Dicerna intends to initiate phase 1 trials for DCR-PH1 in 2015.

FDA approves Flamel's Vazculep
Shares of Flamel Technologies are up more than 5% in pre-market trading this morning, after the FDA approved Vazculep, a treatment for clinically important hypotension in an operating room anesthesia setting. Flamel also secured approval of Bloxiverz, an intravenous drug which reverses the effects of non-depolarizing neuromuscular blocking agents after surgery, last June.

Flamel launched Bloxiverz during the first quarter of 2014, which contributed to a 78.5% year-over-year gain in total revenues to $9.2 million. Flamel's stock has rallied over 100% over the past 12 months.

Merck submits pembrolizumab for approval in Europe
Last but not least, Merck has announced that the European Medicines Agency (EMA) has accepted Merck's marketing authorization application for pembrolizumab (MK-3475), its investigational anti-PD-1 antibody for the treatment of advanced melanoma.

Pembrolizumab is an immunotherapy drug, designed to reactivate anti-tumor immunity in patients. It is currently being evaluated as a potential treatment for over 30 types of cancers as a monotherapy or combination treatment. The company's biologics license application (BLA) for the drug is currently under priority review by the FDA with a PDUFA date of October 28, 2014. The drug has also been designated as a breakthrough therapy for advanced melanoma. Pembrolizumab is expected to generate annual sales of $500 million based on the melanoma indication, and up to $3 billion based on additional indications.