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 -- Novartis (NYSE:NVS), Pfizer (NYSE:PFE), Teva Pharmaceutical (NYSE:TEVA), and Ariad Pharmaceuticals (NASDAQ:ARIA) -- which could loom large in health care headlines this morning.

Novartis' heart failure drug gets rejected in Europe
First and foremost, Novartis' breakthrough heart failure drug serelaxin was rejected by the European Medicines Agency last Friday. Serelaxin, which is intended to be sold under the brand name Reasanz, is a key part of Novartis' strategy to diversify its portfolio away from Diovan, its blockbuster blood pressure drug which went off patent last year.

Novartis does not intend to give up its pursuit of a European approval, and has stated that it will submit a "revised filing package" to support the drug's application for approval. Novartis is hoping for a conditional approval upon reexamination, which means that Novartis might be allowed to market the drug while continuing additional late-stage trials.

If approved, Novartis forecasts annual peak sales of $600 million to $1.0 billion for the drug.

It wasn't all bad news in Europe for Novartis, however. The Committee for Medicinal Products for Human Use (CHMP) recommended the use of Novartis' asthma drug Xolair as a treatment for a chronic form of hives, specifically in adults and adolescents at least 12 years old who do not respond well to H1 antihistamines. Novartis is currently partnered with Roche's Genentech unit in the marketing of Xolair.

Teva's MS pill gets rejected in Europe
Teva also suffered a major setback in Europe, after the CHMP voted against the marketing authorization of laquinimod, its experimental multiple sclerosis (MS) pill. The CHMP reasoned that animal studies showed that the drug showed a higher occurrence of cancer in animals and posed the risk of fetal harm.

Laquinimod, also known as Nerventra, had already shown disappointing results during clinical trials in 2011, which prompted Teva to not seek out an FDA approval until further trials could be conducted.

Although the outcome wasn't unexpected, it was disappointing, since Teva is being weighed down by major concerns regarding its injected MS treatment, Copaxone, which accounts for a fifth of its top line.

In addition to the threat of oral MS drugs such as Biogen's Tecfidera, Novartis' Gilenya, and Sanofi's Aubagio, the patent for Copaxone expires in May -- leaving it vulnerable to upcoming generic versions from Mylan and Momenta Pharmaceuticals.

Despite the setback, Teva and its partner Active Biotech are initiating a new study, named Concerto, to test laquinimod's ability to slow disease progression in MS patients. If the tests are successful, Teva expects the drug to reach the U.S. market by late 2017 or early 2018.

Pfizer's lung cancer drugs fails two late-stage studies
Meanwhile, Pfizer just announced disappointing top-line results from two phase 3 studies of dacomitinib, its experimental drug for advanced non-small cell lung cancer (NSCLC). Unfortunately, both trials failed to meet their primary endpoints.

Dacomitinib attempts to treat NSCLC by preventing autophosphorylation, a process which may lead to unregulated cell division and tumor growth.

The first trial, which compared dacomitinib to erlotinib (Roche's Tarceva), did not show a statistically significant improvement in progression-free survival rates. The second trial, which compared the drug to a placebo, failed to show an improvement in the overall survival rate in patients on which both chemotherapy and a tyrosine kinase inhibitor (such as Tarceva) had previously failed.

An ongoing third trial, however, is evaluating dacomitinib in a different population of treatment-naive patients with EGFR (epidermal growth factor receptor) mutations in NSCLC. Results from that trial are expected by 2015.

Although this is a setback for Pfizer's growing oncology pipeline, it's only a minor one. The company still has two high-growth cancer drugs -- Xalkori and Inlyta -- in its portfolio, along with palbociclib, a promising new breast cancer treatment which could generate peak sales of $1.9 billion if approved.

Takeover buzz continues for Ariad
Last but not least, investors should keep an eye on Ariad, which became highly volatile at the end of last week due to acquisition rumors.

Ariad fell off a cliff last October, after the FDA pulled its only marketed product, the blood cancer drug Iclusig, off the market amid safety concerns regarding cardiovascular events. The stock stabilized after the FDA allowed Ariad to continue marketing Iclusig with a revised label on December 20, but peak sales estimates of $1.4 billion by 2023 will likely be revised.

Although the worst seems to have passed for Ariad, the stock is still down more than 50% over the past twelve months. According to a recent Bloomberg report, Ariad has attracted interest from Eli Lilly (NYSE: LLY), GlaxoSmithKline (NYSE: GSK), and Shire (NASDAQ: SHPG).

However, investors should take these rumors with a grain of salt -- if they amount to nothing, Ariad could give up its recent gains (including its nearly 20% rally on Friday) in a hurry.

 

Fool contributor Leo Sun has no position in any stocks mentioned. The Motley Fool recommends Momenta Pharmaceuticals and Teva Pharmaceutical Industries. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.