Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares in Advaxis Inc.(ADXS) jumped by 17% today after the company announced that patient enrollment is under way for an early stage trial that will study its ADXS-PSA immunotherapy alongside Merck & Co's Keytruda as a treatment for prostate cancer.

So What: The study will enroll 51 previously-treated patients who are diagnosed with metastatic castration-resistant prostate cancer.

The trial will include an arm in which patients will receive ADXS-PSA as a monotherapy and another arm in which patients will receive the two drug combination. The early stage trial's primary endpoint is safety and tolerability, which is typical for early stage studies. However, secondary endpoints for anti-tumor activity and progression free survival could also provide insight into whether this therapy could improve patient outcomes.

Now What: ADXS-PSA is an immunotherapy that is designed to stimulate an immune system response to PSA. In preclinical trials, combining ADXS-PSA with Keytruda showed signs of anti-tumor activity, but pre-clinical research often doesn't translate into successful human trials. Historically, more than 90% of drugs entering human trials fail to make it to commercialization.

That suggests that the odds are stacked against Advaxis and that investors ought to approach it with a healthy dose of caution. Since it will be a while before we know the outcome of this study, investors may want to be patient and wait to see the trial results from this study, or the results from Advaxis' phase 2/3 trial of ADXS-HPV as a treatment for anal cancer, before chasing this stock higher.