(R)-vanzacaftor potentiates BK_Ca channels in the absence of CFTR correction or potentiation

We previously demonstrated the CFTR correctors VX-445 (elexacaftor) and S-VX-121 (vanzacaftor) potentiate heterologously expressed BK_Ca channels, as well as in primary human bronchial epithelial cells (HBEs). This potentiation of BK_Ca resulted in altered vasoreactivity and neuronal excitability. We postulated novel compounds could be identified that would potentiate BK_Ca while not affecting CFTR. Herein, we demonstrate that the enantiomer of vanzacaftor, R-VX-121, possesses these attributes. Using Fisher rat thyroid (FRT) cells expressing F508del CFTR, we demonstrate S-VX-121 corrects F508del CFTR when incubated overnight, as assessed by an increase in transepithelial Cl^- current (I_Cl) in response to forskolin, as well as the appearance of band C upon immunoblot (IB). In contrast, R-VX-121 failed to increase I_Cl and induce band C. Importantly, R-VX-121 competed with S-VX-121 to eliminate the correction of F508del CFTR observed during both I_Cl measurements and IB, indicating it associates with CFTR. Neither S- nor R-VX-121 potentiated CFTR, as assessed by changes in I_Cl. Distinct from our CFTR results, both S- and R-VX-121 potentiated BK_Ca in primary HBEs as well as during whole cell patch-clamp recording of heterologously expressed α-BK_Ca. Using wire myography, we demonstrate both S- and R-VX-12 vasodilate preconstricted mouse mesenteric arteries in a paxilline-dependent manner, confirming a role for BK_Ca. In contrast, the CFTR inhibitor, CFTR_inh172 did not alter the effects of S- and R-VX-121 on vasoreactivity, confirming CFTR is not involved in this response. These data demonstrate R-VX-121 represents a novel BK_Ca potentiator that does not modulate CFTR function, suggesting R-VX-121 may be clinically useful as a BK_Ca agonist.NEW & NOTEWORTHY We previously demonstrated that the CFTR correctors, VX-445 and S-VX-121, are BK_Ca channel potentiators. These CFTR correctors altered vasoreactivity and action potential firing frequency effects, which may explain the adverse events (AEs) reported in cystic fibrosis (CF). We now demonstrate that the enantiomer of vanzacaftor, R-VX-121, potentiates BK_Ca, while not correcting or potentiating CFTR. Thus, we have identified a novel BK_Ca potentiator that may be useful in diseases where BK_Ca modulation is therapeutically proposed.