Paratek Shares Climb After Antibiotic Clears First Phase 3 Hurdle

Xconomy Boston — 

Paratek Pharmaceuticals has stuck with its antibiotic omadacycline over the years, even as three of the company’s pharmaceutical partners bailed on the drug. Today the Boston company has taken a key step closer to proving it made the right call.

Paratek (NASDAQ: PRTK) said this afternoon that omadacycline hit all its main and secondary goals in a late-stage trial of 645 patients with certain types of bacterial skin infections. Those goals were for omadacycline to perform at least comparably to—not necessarily better than—the antibiotic linezolid (Zyvox) on measures such as its ability to reduce the size of lesions from these infections within two to three days, or to improve patients’ overall condition.

On those fronts, Paratek says omadacycline has succeeded. The “early clinical response” rate—within two to three days of taking the drug—was 84.8 percent, compared to 85.5 percent for linezolid. The threshold for success was for omadacycline to be within 10 percent of linezolid. Omadacycline’s other main goal was to improve or clear symptoms seven to 14 days after their final dose, and the drug performed slightly better than linezolid, according to a statement from Paratek.

The most common side effects were gastrointestinal problems such as nausea, vomiting, and diarrhea. There were more serious treatment-related side effects for omadacycline—3.4 percent of patients, compared to 2.5 percent of patients on linezolid—but Paratek said they weren’t considered to be related to the drug. The company didn’t specify what the side effects were; it will detail more data at an upcoming medical meeting.

Shares of Paratek climbed 18 percent in after-hours trading on Wednesday, to $19.40 apiece.

There are a number of approved antibiotics for what are known as acute bacterial skin and skin structure infections (ABSSSI), which lead to some 750,000 hospitalizations each year.

But Paratek chief commercial officer Adam Woodrow says they’re all “narrow spectrum” treatments that are “almost exclusively” taken intravenously. Omadacycline is being developed both as an IV treatment and once-a-day pill. The trial discussed today started with patients who needed IV treatment at first, then switched to a pill once their condition stabilized.

It’s also a “broad spectrum” drug, he says, meaning it can handle multiple types of infections including gram-negative bacteria, which have a cellular membrane that other bacteria don’t and are tougher to deal with.

Paratek has another big hurdle to clear before it can file for approval. A second Phase 3 trial of omadacycline in patients with hospital acquired pneumonia is underway, and Paratek must succeed in that study as well to make its case to regulators. Such success is no guarantee—fellow antibiotic developer Tetraphase Pharmaceuticals (NASDAQ: TTPH), for instance, also had to succeed in two non-inferiority studies, but failed the second one and now has to run another trial.

If omadacycline succeeds, it will have done so in spite of a strange path for Paratek. The company had three different partners for the drug—first Bayer, then Merck, and lastly Novartis—and each deal fell apart for one reason or another. Paratek then tried to file for an IPO in 2012, but then pulled the offering a year later. It went public in 2014 thanks to a reverse merger with Transcept Pharmaceuticals.

Paratek is holding a conference call this afternoon to discuss the data.