SPR720: Non-tuberculous Mycobacterium

SPR720:  An Oral Antibiotic Designed to Treat Nontuberculous Mycobacterial Pulmonary Disease, a Rare Orphan Disease

Nontuberculous Mycobacterium (NTM) pulmonary disease is a growing global health concern and major unmet medical need due to a lack of new medications being developed to combat these bacteria.

NTM are ubiquitous environmental pathogens that can cause progressive lung damage and respiratory failure, particularly in patients with compromised immune systems or underlying pulmonary disorders.  Although rare, the incidence of NTM pulmonary disease is increasing worldwide. It is estimated that approximately 130,000 patients suffer from NTM in the U.S. and Europe, a figure that is growing at a rate of 8% annually. The elderly and people with compromised immune or lung function are at greatest risk, as are patients with bronchiectasis for whom it is estimated that up to 50% may also have active NTM pulmonary disease.

Treatment of NTM pulmonary disease requires prolonged therapy (continuing for approximately 12 to 24 months) with a combination of drugs approved for other infections and is frequently complicated by tolerability and/or toxicity issues. There are currently no oral antibiotics specifically approved for use to treat NTM pulmonary disease. NTM is also associated with high healthcare costs and high mortality. In 2014, the annual cost in the U.S. alone was estimated at $1.7 billion.

Spero Therapeutics is developing SPR720, a novel, investigational oral agent to treat NTM pulmonary disease.

SPR720 is an orally administered investigational antibacterial agent being developed for the treatment of NTM pulmonary disease. If approved, SPR720 will represent a novel class of antibacterial agents that target enzymes essential for bacterial DNA replication.  

The clinical development of SPR720 is supported by data from its first-in-human Phase 1 clinical trial of SPR720 in healthy volunteers and pharmacokinetic/pharmacodynamic data that suggested predicted therapeutic exposures could be attained with a 500 – 1,000 mg once daily oral dose. Pre-clinical in vitro and in vivo studies have demonstrated potency for SPR720 against Mycobacterium tuberculosis (TB) and a range of bacteria that cause NTM infections, including Mycobacterium avium complex and Mycobacterium abscessus.

In February 2021, the SPR720 program was placed on a clinical hold by the FDA following a review of data from a non-human primate (NHP) toxicology study in which mortalities with inconclusive causality to treatment were observed. In January 2022, the FDA made the decision to lift the clinical hold following Spero’s submission of a comprehensive study report with detailed analyses from the NHP toxicology study. Spero engaged with the FDA in Q1 of 2022 to discuss the re-initiation of the SPR720 Phase 2 trial for NTM-pulmonary disease (NTM-PD) patients, with an expected Phase 2 study start date commencing in the second half of 2022.

  • Potential to be the first approved oral agent for NTM.

    SPR720 is a broad spectrum, oral candidate that, if approved, may be applicable to both non-refractory and refractory patients. Once daily dosing is supported by clinical and non-clinical studies.


  • Potential to address a large unmet need in NTM disease.

    In NTM, treatment failure is common and the current treatment for NTM is lengthy and involves combination therapy, often including three or more antibiotics, including injectables.


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