Programs Designed to Address Unmet Needs in Infectious Diseases

Spero Therapeutics’ antibiotic pipeline is focused on areas for which the unmet medical need is greatest, the biological rationale for treatment is clear, and for which there are few approved therapies, or where the standard of care is suboptimal.

Our pipeline of anti-infective agents is one of the most unique in the industry and consists of four complementary product candidates, including:

• SPR994 Oral Gram-Negative Program is a first in class oral carbapenem that has demonstrated potent in vitro and in vivo activity against a wide variety of Gram-negative bacterial infections, including those harboring drug-resistant extended-spectrum beta-lactamases (ESBLs).
• IV Potentiator Platform, which includes SPR741 and SPR206, is our technology designed to treat serious and life-threatening multi-drug resistant Gram-negative pathogens, such as Enterobacteriaceae, with combination therapies.
• SPR720, a candidate oral antimicrobial agent being developed for the treatment of non-tuberculous mycobacterial (NTM) lung infections.

The following table illustrates our product candidates, their status, and anticipated milestones for ongoing development.

Product Candidate Pipeline and Anticipated Milestones

Information as of January 29, 2019

This chart contains forward-looking statements. Our planned development activities and anticipated milestones are based on our current assumptions, estimates and plans, which may change.