The health care sector exploded with major news events yesterday, fueled by second-quarter earnings, clinical trial updates, and even unexpected regulatory events.

Given that the day's headlines seemed to be dominated by Puma Biotechnology's stunning 295% pop and Gilead Sciences' (GILD -1.71%) revenue bonanza in the second-quarter, there are undoubtedly some important stories that got buried under this avalanche of news. With that in mind, let's take a look at three huge stories investors might have missed yesterday.

Inovio reports positive mid-stage results for VGX-3100
Inovio Pharmaceuticals (INO -1.46%) released the long-awaited mid-stage results for its DNA-based vaccine VGX-3100 yesterday as a potential treatment for cervical intraepithelial neoplasia 2/3 (CIN2/3).

By the looks of it, Inovio fans didn't miss this pivotal news given that shares soared by over 17% on heavy volume. Even so, the company's market cap at the end of the day still stood well below its peers in the vaccine development business at around $788 million. Put simply, the broader market either wasn't paying attention or perhaps it wasn't impressed with the results. Time will tell. 

Digging into the press release, we learned that VGX-3100 led to histological regression in 53 of 107 women treated with the vaccine compared to 11 of 36 receiving a placebo. According to the company, this difference was statistically significant, warranting a late-stage study of the vaccine. Most importantly, this result provides some of the first hard evidence that DNA-based vaccines may yet have a place in the clinic for use in humans.  

Gilead's new cancer drug overshadowed by Sovaldi
On a busy day for Gilead, the company announced that its blood cancer drug, Zydelig, received accelerated approval by the Food and Drug Administration as a treatment for relapsed chronic lymphocytic leukemia, relapsed follicular B-cell non-Hodgkin lymphoma and small lymphocytic lymphoma. Even so, this major milestone for the company in the field of oncology was vastly overshadowed by the record-breaking sales performance of Sovaldi.  

Although Zydelig will be employed as a second or third-line therapy depending on the specific cancer type, it is still expected to generate sales close to $700 million a year. Put simply, this is a new drug in Gilead's portfolio worth keeping tabs on going forward. 

According to Gilead's second-quarter earnings release, the company is ready to begin promoting the drug immediately, and it's on track to potentially gain approval in Europe as well. As such, we'll probably see Zydelig contribute to Gilead's top-line growth before year's end.

GlaxoSmithKline has one of its worst quarters in recent history
Shares of GlaxoSmithKline (GSK -2.56%) fell by nearly 6% yesterday after the company reported dismal second-quarter numbers and lowered its outlook for the remainder of the year. Yesterday's drop was the stock's biggest decline in nearly six years.

As I previously mentioned, Glaxo is facing a host of problems, including generic competition for former star products like Lovaza, weak commercial performance of new respiratory medicines, and of course, the ongoing Chinese probe. And yesterday's report, we also learned that a strong pound is hurting profitability on U.S. product sales in a big way, with pharmaceutical and vaccine revenues in the U.S. dropping by 10%.  

Foolish wrap-up
The fast and furious pace of yesterday's news might have pushed these stories off the front page, but their importance going forward shouldn't be overlooked by the investing community. Inovio's clinical breakthrough could drive shares much higher as it continues to develop additional products based on this same technology. And Gilead's FDA approval for Zydelig marks the company's entry into the growing oncology market, where it is developing a host of intriguing clinical candidates. Finally, Glaxo's slumping product sales and unfavorable exchange rates are certainly key issues for investors to keep track of moving forward.