Safety, tolerability, and concordance with interferon-γ release assays of a recombinant ESAT6–MPT64 skin test: a phase 1 randomized clinical trial

BackgroundAccurate and cost-effective screening for Mycobacterium tuberculosis (Mtb) infection remains a global challenge. While Interferon-γ Release Assays (IGRAs) offer high specificity, their widespread deployment is hindered by high costs and technical complexity.

Conversely, the traditional Tuberculin Skin Test (TST) lacks specificity due to BCG cross-reactivity. Emerging recombinant skin tests predominantly rely on the ESAT6-CFP10 antigen combination.

To potentially broaden the antigenic repertoire and enhance diagnostic sensitivity, we developed a novel recombinant fusion protein incorporating MPT64 (from Region of Difference 2, RD2) alongside ESAT-6. This study represents the first-in-human evaluation of the ESAT6-MPT64 (EM) skin test.MethodsThis single-center, randomized, open-label, dose-escalation Phase 1 clinical trial (Registration: ChiCTR2500112887) enrolled 60 participants, comprising 30 healthy controls and 30 patients with active pulmonary tuberculosis (TB).

Participants were stratified and randomized into low-, medium-, and high-dose cohorts (n = 10 per cohort/group). The primary endpoint was safety and tolerability.

Secondary endpoints included diagnostic performance (sensitivity and specificity) and concordance with the T-SPOT.TB assay (IGRA).ResultsThe EM skin test demonstrated an excellent safety profile.