Battle of biotech conferences: Neurology and Cancer
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Biotech investors are going to be busy this weekend and into early next week. Two medical conferences kick off Saturday, bringing data on drugs for Alzheimer's, cancer and rare genetic disorders. Here's what analysts are watching.

American Academy of Neurology – April 18-25, Washington, D.C.

Biogen: The biotech giant captured investor attention in December with its early data on experimental Alzheimer's drug BIIB037, or aducanumab, and expectations were high into a March release of further results. Biogen didn't disappoint, showing benefits both on clearing the amyloid plaques associated with Alzheimer's, and on cognition, the memory loss that is a hallmark of the disease. Read MoreBiogen Alzheimer's drug shows promise

While some initial data were released Friday, Biogen is expected to report further incremental details from that study at AAN, providing a glimpse into which patients benefited and how that affected the study results. "Given the enormous ($20 billion-plus) market potential of aducanumab in Alzheimer's, investors are eagerly awaiting any details of the drug's development," analysts at Cowen wrote in an April 16 research note. They said the data investors are most anticipating—on a middle dose of 6 milligrams, hoped to provide the right balance of efficacy and safety—are likely to come later in the year. Citi anticipates those results could come at the Alzheimer's Association International Conference in July. "Overall, we think as much as plus or minus $50 per share could be riding on the long-term results from the 6 mg cohort," Cowen wrote.

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PTC Therapeutics: Bigger stock movements often come from smaller companies, and PTC is among those that analysts are watching. The company is expected to report early data on its drug for spinal muscular atrophy, a rare, debilitating genetic disease that can be fatal by age 2 in its severest forms. Read MoreBig pharma M&A may keep booming, CEOs say

PTC's drug, RG7800, is partnered with Roche, and Cowen says it could potentially present competition to a more advanced compound being developed by Isis Pharmaceuticals and partner Biogen. One main difference: PTC's medicine is taken orally, while Isis' is injected into the spinal fluid. Friday saw some initial details released, confirming the drug's safety and efficacy so far. RBC's Simos Simeonidis wrote in a research note, "the true therapeutic potential of the drug will become clearer, first, once the full dataset is presented at AAN." Alnylam and Isis: Both biotechs are working on medicines for a rare genetic condition known as TTR amyloidosis, with updates expected at AAN. Leerink's Michael Schmidt said he expects Alnylam's data as more meaningful, while Isis', he wrote in an April 16 research note, could be more incremental.

American Association for Cancer Research – April 18-22, Philadelphia

Merck and Bristol-Myers: Though AACR typically features earlier-stage data, the conference this year is setting up to be a preview to the big cancer research show, ASCO (the American Society of Clinical Oncology meeting, held at the end of May in Chicago). Immuno-oncology, the field of medicine that harnesses the immune system to fight cancer, will be front and center, with analysts watching key data on drugs from both Merck and Bristol-Myers in the space. Read MoreCNBC Explains: Immuno-what?

Bristol-Myers' stock rose Friday on separate news that a study in lung cancer of its approved immunotherapy drug Opdivo was stopped early after showing an improvement in survival compared with an older therapy. At AACR, analysts are closely watching data from a combination study of Bristol drugs Yervoy and Opdivo, as well as a comparison study of Merck's Keytruda and Bristol's Yervoy in melanoma. Merck said that study was stopped early at the end of March as Keytruda pulled ahead, and further data are expected to be presented at AACR.