Trial design of bacteriophage therapy for nontuberculous mycobacteria pulmonary disease in cystic fibrosis: The POSTSTAMP study.

Bacteriophages (phages) are viruses that selectively infect bacteria and have been utilized to treat Mycobacterium abscessus (Mab) with varying success. The POSTSTAMP study is an ongoing, multi-site phage therapy protocol for treatment-refractory pulmonary Mab disease in people with cystic fibrosis (pwCF). Participants (n = 10) are prospectively assessed while utilizing FDA investigational new drug (IND) approval for compassionate use. Participants are >6 years old, able to produce sputum, have been treated with guideline-based antibiotic therapy (GBT) for >12 months without culture conversion, and are currently receiving GBT with at least 3 and ≥ 80 % positive Mab cultures in the prior year. At enrollment, an isolate is assessed for the availability of lytic phage(s). Open-label phage therapy consists of 1 or 2 phages administered intravenously twice daily for 52 weeks. Participants without a phage match will be followed on GBT as a comparison group. Follow-up visits will occur monthly, with one follow-up visit at completion and intermittent visits for a year after phage therapy. Efficacy will be assessed by culture, standard clinical measures and a patient-reported quality-of-life instrument. Frequency of Mab detection 12 months prior to treatment will be compared with the 12-month period beginning 6 months after treatment initiation. Individual-level tests of difference in percent positive cultures within subjects will be used to identify "responders". Collectively and including all persons, a mixed-effect model will be used to test for a difference in frequency of Mab detection following treatment or without treatment. The trial will also test for markers of treatment failure and pathogen adaptation in participants who did not achieve microbiological response, and will monitor for safety and tolerance.