Spero plans to have two antibiotics for resistant pathogens in pivotal trials next year

Spero is expecting an accelerated path to market based on unmet needs its products are addressing

Buoyed by a third-round fundraising that netted $51.7 million, antibiotic developer Spero Therapeutics says it will be able to accelerate clinical development of two programs for drug-resistant infections.

The Cambridge, Massachusetts-based company—a 2014 Fierce 15 firm—is focusing on new antimicrobials that target drug-resistant infections, and Spero's president and chief executive, Ankit Mahadevia, M.D., says it is working to address all the most serious pathogens detailed by the World Health Organization (WHO) in a hit list last month that aimed to draw attention to "practically dry" antibiotic pipelines in the biopharma industry. 

"Both of Spero's lead programs address multiple Gram-negative bacteria, including two bacteria listed as 'critical' by the WHO—Enterobacteriaceae and Acinetobacter baumanii," Mahadevia told FierceBiotech via an email interview.

Lead candidate SPR741, the most advanced candidate in Spero's Potentiator program of hospital-based medicine combinations, started a phase 1 single ascending dose/multiple ascending dose (SAD/MAD)  trial in December which is scheduled to complete in the second quarter of the this year.

Potentiator aims to improve existing antibiotics by enabling them to pass through the cell membrane of Gram-negative bacteria. According to Mahadevia, SPR741 "increases the spectrum and potency of more than two dozen classes of Gram-positive antibiotics to include activity against multidrug resistant Gram-negative infections when used in combination."

Combination studies involving SPR741 should start by end of 2017 with a two-pronged approach—a large double-blind trial in complicated urinary tract infections (cUTIs) as well as an open-label target pathogen study.

Second candidate SPR994 is a novel oral agent that has shown activity against a wide variety of Gram-negative bacteria in early studies, including extended spectrum beta lactamases (ESBLs), which are also on the WHO list, according to the CEO.

Spero's not prepared to disclose its mechanism just yet, but Mahadevia said it has demonstrated a favorable safety and pharmacokinetic profile in humans outside the U.S.. The drug could be used "both in the hospital and in the community, [and] could be appropriate for over a million patients, based on today's cUTI market," he added.

Pivotal studies for both the SPR741 and SPR994 programs are expected to begin in early 2018, and while Spero reckons it will get an accelerated regulatory path, it is not speculating yet on when it may be able to bring them to market, or indeed its commercialization plans.

"With several programs in the pipeline at once, Spero has the option of partnering some of our programs, as well as commercializing some on our own," said Mahadevia. There was also no comment on any plans to go public, but he CEO suggested that the Series C round "gives Spero the runway to explore all funding options."

Google's venture capital arm GV led the latest fundraising as a new investor, along with RA Capital Management and Rock Springs Capital.

"Spero is working on one of the greatest unmet needs in medicine—developing antibacterial treatments for some of the most resistant infections patients today," said GV general partner Krishna Yeshwant.

"The company has assembled a team with the proven ability to bring new antibacterials to the market, and has made remarkable progress in building a differentiated pipeline in a short period of time."