There's one drawback to having the stock market indexes hit record highs yet again: It makes finding truly horrendous health-care stocks for our weekly series much more challenging. But the Fool is always up for a good challenge, so here are three stocks that missed out on the celebration this week.

Infinity sees its limits
Infinity Pharmaceuticals
(NASDAQ:INFI) ranks as the biggest loser for the past week. Shares fell more than 22%.

There wasn't any major news from Infinity over the past five days that caused its stock to go negative. Instead, investors appear to be increasingly anxious over the company's upcoming presentation of clinical data related to its phase 1 trial of experimental drug IPI-145 and release of data later this year for retaspimycin HCl in treating lung cancer.

Such skittishness was probably exacerbated by a couple of announcements this week from other companies developing leukemia drugs. Roche announced good results from a study of its drug GA101, which targets chronic lymphocytic leukemia, or CLL.

Likewise, Gilead Sciences (NASDAQ:GILD) released positive findings from its early-stage study of idelalisib. The drug showed promise in shrinking tumors and increasing progression-free survival. Gilead now has five late-stage trials for idelalisib for CLL and indolent non-Hodgkin's lymphoma.

Finding a silver lining
(NASDAQ:ONTY) announced disappointing clinical results on Thursday for experimental cancer drug L-BLP25, previously known as Stimuvax. The stock dropped nearly 21% for the week.

The bad news from Oncothyreon was that L-BLP25 didn't meet the primary endpoint of the phase 3 study for the treatment of advanced non-small-cell lung cancer. Patients taking the drug had a median overall survival rate of 25.6 months, compared with 22.3 months for those taking placebo.

Even though this wasn't what the biotech hoped for, Oncothyreon did find a silver lining. A subset of patients receiving concurrent chemoradiotherapy did live longer. These patients had a median overall survival rate of 30.8 months, versus 20.6 months for patients in the control arm.

Horrendous "lite"
Synageva BioPharma
(NASDAQ:GEVA) rounds out this week's list of horrendous health-care stocks. Really, though, the biotech's performance wasn't all that bad. Shares fell around 7% for the week. That's more like horrendous "lite."

However, the past three weeks have been horrendous for Synageva. The stock has plunged 27% during this period. This week appeared to be carryover from investors who dumped shares over the past few weeks.

Some of Synageva's woes can be seen in its quarterly results announced on May 7. The biotech lost nearly twice as much as it did in the same period of 2012. J.P. Morgan also downgraded the stock last week over concerns that Synageva could have problems enrolling patients for its late-stage clinical study of sebelipase alfa for treating adults with late-onset Lysosomal Acid Lipase Deficiency.

A good week
You know it's been a good week for the market when any of the most horrendous health-care stocks drop by only a single-digit percentage. There usually are more stocks dropping by 15% or greater than we have room to discuss. The opposite was true for this week, with plenty of health-care stocks gaining by 15% or more.

We shouldn't get used to it, though. There will be plenty of horrendous weeks and truly horrendous stocks in the months ahead.

Fool contributor Keith Speights has no position in any stocks mentioned. The Motley Fool recommends Gilead Sciences. Try any of our Foolish newsletter services free for 30 days. We Fools don't 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.