Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

Good morning, fellow Foolish investors! Let's take a look at four stocks that are worth watching today -- Sanofi (SNY -0.47%), Salix Pharmaceuticals (NASDAQ: SLXP), Akorn (AKRX), and Isis Pharmaceuticals (IONS -0.60%). Let's check in on the recent developments regarding these companies.

Sanofi reports another setback in oncology
Sanofi has announced that it is halting all clinical trials for its investigational JAK2 inhibitor, fedratinib. The drug was intended to treat three types of blood and bone marrow disorders -- primary myelofibrosis, polycythemia vera, and essential thrombocythemia.

The discontinuation came after the drug was put on clinical hold by the Food and Drug Administration due to safety concerns. Sanofi stated that the risks that fedratinib posed to patients did not outweigh the benefits.

If approved, fedratinib would have strengthened Sanofi's oncology portfolio, which could have diversified the company away from its five largest businesses -- diabetes, vaccines, consumer health, animal health, and Genzyme (rare diseases).

It won't be a major loss for Sanofi, since peak sales of the drug had only been pegged at $226 million by 2017, but it represents yet another major setback in oncology for the company. Last month, Sanofi and Merrimack Pharmaceuticals' non-small-cell lung cancer drug candidate, MM-121, failed to meet its primary endpoints in a phase 2 trial.

For now, Sanofi investors shouldn't fret about the news, although it represents yet another missed opportunity to diversify its drug portfolio away from its two highest growth businesses -- diabetes and Genzyme.

Salix gains FDA approval for additional indications for Deflux
Salix Pharmaceuticals announced today that Deflux, its treatment for vesicoureteral reflux grades II-IV in children, had been approved by the FDA for two new injection techniques -- a single intra-ureteric injection and a double intra-ureteric injection. VUR is the abnormal flow of urine from the bladder into the upper urinary tract, which can cause kidney damage and failure.

This new approval will increase the possible uses of Deflux, which accounted for 6% of Salix's top line last quarter. 70% of Salix's revenue is generated by Xifaxan, a treatment for traveler's diarrhea.

This recent development is just another bit of good news for the company, which shook up the markets earlier this month when it acquired Santarus for $2.6 billion -- a move that wisely boosted its presence in the diabetes market while decreasing its dependence on Xifaxan.

Shares of Salix have soared 130% over the past 12 months and are currently perched at all-time highs.

Akorn adds three more eye treatments to its ophthalmics portfolio
Another story to follow up on today is Akorn, which soared 8% into the close last Friday after it announced that it had acquired three eye-drop brands from Merck (MRK 0.37%) for $52.8 million.

The deal adds two versions of the glaucoma treatment Cosopt and the bacterial conjunctivitis treatment AzaSite to Akorn's portfolio, which the company expects to add $34 million to $38 million in annual revenue and $0.09 to $0.11 in earnings per share by next year.

Last year, Akorn reported $255 million in revenue -- an 86% jump from the previous year, thanks to robust sales in its ophthalmics and injectables businesses. In October, Akorn nearly doubled in size by acquiring ophthalmic company Hi-Tech Pharmacal for $640 million.

Now with three new treatments now added to its portfolio, Akorn's strong revenue growth looks to continue into next year, and investors agree -- the stock is up more than 80% over the past 12 months and currently sits at all-time highs.

Isis investors get more good news
Last but not least, Isis Pharmaceuticals announced positive results from a phase 1 study of ISIS-APO(a)Rx -- a treatment to lower levels of Lp(a), or lipoprotein(a), which has been associated with increasing the risk of cardiovascular disease and heart attacks. According to the company, patients achieved dose-dependent reductions of up to 95% in Lp(a) levels.

Isis is a development-stage company that specializes in using its RNA-based novel drugs to treat major diseases such as diabetes, asthma, and cardiovascular diseases.

This is the third bit of good news that Isis investors have received over the past week. On Tuesday, the company announced that it had received a $1.5 million milestone payment from Biogen Idec for positive progress made in its phase 2 study of its treatment, ISIS-SMNRx, in infants with spinal muscular atrophy. Then on Friday, Isis stated that it had received a $5 million milestone payment from GlaxoSmithKline for the development of its ocular disease treatment, ISIS-GSK4Rx.

By itself, Isis only has a single marketed product -- the homozygous familial hypercholesterolemia (HoFH) treatment Kynamro, which was co-developed with Sanofi's rare disease unit, Genzyme. The remainder of its revenue growth is completely driven by milestone and collaboration payments. In addition to Biogen and Glaxo, Isis also collaborates with AstraZeneca, OncoGenex, and Teva Pharmaceutical.

Last quarter, Isis' revenue climbed 103% from the prior-year quarter, although it remains unprofitable. Its stock has risen nearly 300% over the past 12 months, based on optimism regarding upcoming milestone payments from collaborating companies.