Halloween week brought plenty of treats for some investors. These three health-care stocks scored big and didn't even have to wear a costume.

Sweet pipeline?
You might expect Mr. Market to scream "boo!" after a company misses revenue and earnings estimates. That didn't happen with Idenix Pharmaceuticals (NASDAQ: IDIX), though. Shares jumped 26% for the week after a huge 44% rally on Friday.

Investors shrugged off paltry revenue for the third quarter and a loss of $0.25 per share. Instead, all eyes were on the pipeline update. Idenix reported that all patients have been enrolled in the first part of a phase 2 study of its hepatitis-C virus, or HCV, drug samatasvir combined with simeprevir, which is being developed along with Johnson & Johnson's (JNJ -1.15%) Janssen division and Medivir.  

Idenix and J&J now plan to move forward with a second mid-stage trial including samatasvir and semeprevir along with TMC647055, another drug developed by Janssen. Idenix also announced that HCV drug IDX21437 received approval to move into early stage clinical trials in Belgium and Canada. 

HAE heyday
Dyax (NASDAQ: DYAX) was another biopharmaceutical company reporting third-quarter financial results that few really cared too much about. Shares surged nearly 20% -- driven more by pipeline interest more than any financial numbers.

Revenue did increase during the quarter to $13.7 million as sales of Hereditary Angioedema, or HAE, drug Kalbitor picked up a bit. However, investors were likely more pumped up about other news in the update. One item of note is that Dyax recently initiated an early stage study of another HAE drug, DX-2930.

There was also good news on the licensing front. Lilly (LLY -1.00%) reported last week that the U.S. Food and Drug Administration granted priority review for ramucirumab in treating advanced gastric cancer. Lilly also recently announced positive results from a late-stage study of lung cancer drug necitumumab. Development of both drugs used phage display libraries licensed from Dyax.

Profit prophet
When a company forecasts a profitable year after going a while losing money, it tends to bring smiles to investors' faces. Osiris Therapeutics (NASDAQ: OSIR) shareholders are no doubt beaming after the stock soared nearly 20% this week.

Osiris reported good third-quarter results on Friday. Although it lost $0.05 per share, analysts had expected a much-worse $0.38 per share loss. After more than tripling revenue in the third quarter, Osiris now projects that both the fourth quarter and full year 2013 will be profitable. That's a nice change after losing over $11 million last year.

The company now looks to be on pretty solid financial footing after the third-quarter results and its sale of Prochymal assets. More encouraging news could be on the way if Osiris gains approval for its Biologics License Application, or BLA, for wound repair product Grafix.  

Great pumpkin award
I usually pick the best of the best from our weekly lineup of humongous health-care stocks. Since it's Halloween week, the winner will receive the prestigious but mythical Great Pumpkin Award. And the award goes to ... Osiris Therapeutics. 

Idenix enjoyed a great week, but it still must face some heavyweight competition in the HCV market. Dyax could see more success from its HAE drugs and licensed technology. Osiris, though, gets the Great Pumpkin due to its quantifiable financial improvement and potential for even better days ahead. 

Osiris needs to execute well, though. As Charlie Brown's friend Linus said, "One little slip... could cause the Great Pumpkin to pass you by."