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 of XOMA (NASDAQ:XOMA), a biopharmaceutical company engaged in the development of antibody-based therapies, jumped as much as 20% after receiving an upgrade from MLV & Co. before the opening bell.

So what: According to a report published prior to the opening bell, MLV & Co. analyst Craig Suvannavejh upgraded XOMA to a buy from hold but reiterated his price target of $7 for shares, implying upside of 83% based on yesterday's closing price. While MLV's upgrade came on the heels of steep drop in XOMA's price and was certainly valuation related, it also is based on optimism surrounding expected positive data from XOMA's P3 EYEGUARD-B trial involving gevokizumab for Behcet's uveitis.

Now what: As usual, it's probably not worth placing too much credence into analyst upgrades and downgrades because they're often very short-term share price drivers and rarely do they affect our long-term investment thesis in a company. To add further context to this, keep in mind that on March 11, just a couple of weeks ago, the same MLV analyst downgraded XOMA based on valuation and lowered his firms' price target to $7 from $8. During that report Suvannavejh noted that MLV had witnessed "too many disappointments" with Xoma and wanted "to see more concrete progress" with gevokizumab.

What investors will want to focus on are those "concrete results," and lately they've been unimpressive with gevokizumab failing to advance in trials as a treatment for erosive osteoarthritis of the hand last month. The good news is gevokizumab is being tested in a number of indications, which gives XOMA plenty of chances to hit a home run. I'd certainly suggest this stock isn't for the faint of heart and would much prefer to stick to the sidelines until after its Behcet uveitis data is out, but I can certainly see some promise for gevokizumab based on the sheer number of indications it's being tested to treat.