Preventive Approach to Congenital Heart Block With Hydroxychloroquine

One of the strongest clinical associations with autoantibodies directed to components of the Ro/La ribonucleoprotein complex is the development of congenital heart block (CHB) in an offspring, an alarming prospect facing 2% of primigravid mothers with these reactivities. The risk is 10-fold higher in women who have had a previously affected child. Despite the attempt of large multicenter studies to forestall disease by serial in utero monitoring, irreversible block and extensive myocardial injury have been documented within 7 days of a normal rhythm and PR interval. CHB is associated with a substantial mortality and morbidity. Two recent prospective studies (20 mothers from U.S. and 15 from Europe) utilizing an identical protocol of IVIG at replacement doses demonstrated 1) this intervention does not prevent the recurrence of CHB 2) the recurrence rate of 17-18% is robust 3) recruitment of patients is feasible. During the time period of the IVIG trials, basic science exploring the pathogenesis of disease supported the notion that Toll Like Receptor (TLR) signaling following ligation of ssRNA (hY3) complexed to the Ro protein contributes to fibrosis. This observation led to in vitro studies addressing inhibition of endosomal acidification by chloroquine and subsequent translation to patients by evaluating the use of hydroxychloroquine (HCQ) in an extensive retrospective chart review. The combined data suggest efficacy of HCQ. Accordingly, the goal of this study is to: To determine whether hydroxychloroquine use during pregnancy prevents CHB in a high risk population. The trial is open-label and employs the Simon's 2-stage optimal design to allow for early stopping due to absence of treatment efficacy. The first stage requires 19 subjects. Despite the rarity of disease and the requirement of a previous CHB child, based on the US Research Registry for Neonatal Lupus, this proposal is feasible. If 3 or more mothers have a child with 2nd or 3rd degree CHB, the study is terminated after the first stage. If this does not occur, funds will be sought to enroll an additional 35 mothers in the second stage for a total of 54 subjects. Treatment will be considered efficacious if fewer than 6 mothers of 54 have a child with advanced CHB. With this design, the study has 90% power to conclude that hydroxychloroquine is preventive if the true recurrence rate with the treatment is 5%. In addition, the probability of rejecting the treatment for further study is 95% if the true recurrence rate is 18%. Serial echocardiograms (monitor PR interval) and blood drawing (IFNƒÑƒnsignatures, antibody titers) will be included in the protocol. The results of this study are expected to become an integral part of the counseling of women with anti-SSA/Ro-SSB/La antibodies who are considering pregnancy.