Spero Therapeutics raises $30M to support its drug delivery platform targeting Gram-negative bacteria

Cambridge, MA's Spero Therapeutics has raised $30 million in Series B financing to develop its so-called Potentiator Platform to improve existing antibiotics by enabling them to pass through the cell membrane of Gram-negative bacteria.

Spero CEO Ankit Mahadevia

Gram-negative bacteria have a highly polar and negatively charged lipopolysaccharide membrane that protects them from many antibiotics, the company explains on its website. Spero's "potentiators" are designed to increase the outer membranes' permeability, enabling antibiotics initially intended to treat Gram-positive bacteria to enter the cell.

The 2014 Fierce 15 company plans to soon take its lead potentiator candidate to the clinic, reports Xconomy. It will be co-administered with an undisclosed antibiotic. CEO Dr. Ankit Mahadevia declined to tell the publication whether the candidate will be paired with an approved med or another company's development-stage drug.

In fact, last month the company licensed a class of drugs known as dihydrofolate reductase (DHFR) inhibitors from Montana's Promiliad Biopharma. It intends to deploy them against Gram-negative bacteria, something that "historically DHFR inhibitors haven't been able to do," Mahadevia told Xconomy.

The potentiator platform was itself licensed from Finland's Northern Antibiotics in June 2015, around the time of its $30 million Series A financing, which included investment from Merck Research Ventures.

Several of the Series A investors returned for the Series B round. The financiers were Atlas Venture, SR One, MRL Ventures, Lundbeckfond Ventures, The Kraft Group and Partners Innovation Fund.

"We are very privileged to have the strong support of our existing investors to close this Series B financing, which will allow us to continue to advance the important work we are doing to combat the global public health threat of antibiotic resistance," Mahadevia said in a statement. "Humankind is currently losing a race against bacteria now resistant to every known antibiotic--known as 'Superbugs'--with immeasurable healthcare consequences if left unchecked. Spero is executing an aggressive effort to develop important therapies that differ mechanistically and functionally than available treatments in order to address this growing threat."

Roche ($RHHBY) has the option to acquire the company's MvfR inhibitor program, which targets Pseudomonas and other Gram-negative bugs, at a predetermined price once Spero files for an Investigational New Drug (IND) application.

- read the release
- here's Xconomy's take
- here's more from FierceBiotech

Special Report: FierceBiotech's 2014 Fierce 15 - Spero Therapeutics

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