Cubist’s Calixa Buyout Bears Fruit as Antibiotic Hits First Phase 3 Mark

Xconomy Boston — 

When Cubist Pharmaceuticals (NASDAQ: CBST) agreed to shell out as much as $402.5 million for Calixa Therapeutics a few years ago, this was the type of day it had in mind.

Lexington, MA-based Cubist said today that the antibiotic it acquired in the Calixa buyout, CXA-201, hit its mark in the first of two Phase III trials. In this study, the drug showed to be just as good as the generic antibiotic levofloxacin—and potentially better—at treating patients with complicated urinary tract infections (cUTI). Cubist shares surged about 10 percent on the news.

The 1,050-patient study was designed to test whether the injectable antibiotic could wipe out a cUTI within five to nine days of patients taking their last dose. Cubist hit that mark, and also says it found that the drug performed better, statistically speaking, than levofloxacin—something the trial wasn’t designed to show. Cubist was only hoping to prove “non-inferiority” to levofloxacin, the standard of care for people with a cUTI.

“While positive Phase III data for CXA-201 in cUTI has ben expected, superior efficacy vs. comparator is an unexpected, positive surprise,” Jefferies & Co. analyst Eun Yang wrote in a note to clients this morning.

Cubist didn’t divulge the full numbers proving its claims just yet—it only released top-line results from the study. The full details will be released at a medical meeting next year.

The most common side effects experienced by patients were headaches, constipation, hypertension, nausea, and diarrhea. Cubist said those side effects weren’t any more prevalent than they were in patients taking levofloxacin.

The results are the first of two late-stage studies Cubist is running for CXA-201. It’s also testing the drug in patients with complicated intra-abdominal infections, and plans to release the results of that study in late December. Cubist hopes those data, and the results of the cUTI trial, will give it the juice to file for approval from regulators. It hopes to eventually use the drug to treat people with pneumonia acquired in hospitals as well.

Cubist acquired CXA-201 when it bought San Diego, CA-based based Calixa in 2009. Cubist paid $92.5 million up front and promised up to $310 million more to Calixa shareholders as part of the deal. The drug is a combination of two antibacterial compounds, cephalosporin and tazobactam.