The health-care sector is notorious for the volatility of its stocks. Events such as clinical trial data, partnership agreements, or insurance reimbursement news can have significant effects on share price. Let's look at what specifically caused some of today's biggest market jumps in this space.

First up is pharma giant Eli Lilly (LLY -1.81%). The company has a number of drugs on the market, including the injectable insulin product Humalog and antidepressant Cymbalta. This stock has climbed about 20% year to date, and the stock jumped 5.29% today on news related to its Alzheimer's disease clinical trials. Eli Lilly's developmental drug solanezumab didn't meet the two primary endpoints set for the study, but the new data released today showed that the therapeutic was able to slow down memory loss in early-stage Alzheimer's patients by 34%.

While these results aren't unequivocally positive, this market move reflected hope that solanezumab could eventually become a treatment option for Alzheimer's patients. Eli Lilly stated that it will consider the next steps for this drug in the coming weeks, but its road to FDA approval looks long and winding -- and could involve additional clinical trials. After today's increase, Eli Lilly is perched near its 52-week high, but investors should be on the lookout for upcoming clinical results related to this developmental medicine.

Next, Sequenom (NASDAQ: SQNM) had a healthy 5.1% boost without a particular catalyst, and this was a welcomed respite from what has been a largely disappointing year. Fellow Fool Keith Speights recently analyzed the challenges facing this company and also outlined some important things to for investors to watch. Questcor Pharma (NASDAQ: QCOR), which you might remember dropped by almost 50% last month after receiving bad news from insurer Aetna (AET), rose by 4.59%. This modest gain was the result of a survey done by LifeSci Advisors, which stated that doctors are still planning on prescribing QuestCor's Acthar Gel for the treatment of multiple sclerosis. It remains to be seen whether this is the beginning of turnaround for Questcor or simply a small rebound.

Finally, VIVUS (VVUS), which started marketing its obesity drug Qsymia last month, popped 10.19% today after announcing that Express Scripts signed up to distribute the drug. This opens up an additional distribution channel for VIVUS and will definitely help to increase Qsymia's sales. This is clearly welcome news for shareholders, considering that the stock took hit last month after news that the European Medicines Agency probably won't approve Qsymia for use in the EU.