Predicting Response to Pregnenolone Treatment of Irritability in Autism Spectrum Disorder – Preliminary Neurosteroid Metabolomic Analysis

Background: Pregnenolone (PREG) is the precursor of endogenous pharmacologically active neurosteroids. When orally administered in humans, PREG is converted to multiple metabolites, including allopregnanolone (a GABA_A receptor agonist). We recently reported the results of an open-label trial of PREG in the treatment of adults with autism spectrum disorder (ASD). We found that PREG reduced the levels of irritability and associated aggressive behaviors as measured by the Aberrant Behavior Checklist – Irritability subscale (ABC-I). PREG was also found to be well-tolerated by the study participants.

Objectives: To explore the associations between response to PREG and plasma concentrations of metabolites of PREG before and after 12-week trial of oral PREG.

Methods: PREG was initiated at 50mg twice daily in weeks 1 and 2, then increased by 50mg twice daily every 2 weeks to a final dose of 250mg twice daily which was maintained from weeks 9 to 12. Primary outcome measure was the ABC-I. Response was defined as change of ABC-I of 7 or greater. Concentrations of PREG and its metabolites in plasma samples were quantified by liquid chromatography-mass spectrometry. Analytes measured include PREG, PREG sulfate, progesterone, allopregnanolone, dehydroepiandrosterone (DHEA), DHEA sulfate, testosterone, estradiol, and cortisol. Levels of sex hormone binding globulin (SHBG) in the plasma samples were determined by an enzyme-linked immunosorbent assay (ELISA). Free levels of testosterone were calculated from total testosterone concentration, SHBG concentration, and published values of albumin concentration and association constants of albumin and SHBG. Two-tailed student t-tests were performed to compare metabolite concentrations between responders and non-responders. Regression analyses were also performed to determine the strengths of correlations between the change in ABC-I and the levels of metabolites.

Results: Twelve individuals with ASD (mean age 22.5) participated in this open-label study. PREG yielded improvement in the primary measure, ABC-I [17.4±7.4 at baseline; 11.2±7.0 at 12 weeks (p=0.028)]. Six participants were found to be responders to PREG treatment, while the rest of the six participants did not reach the responder criteria. Mean baseline PREG plasma concentration in the responder group (1.5±0.4ng/mL) was found to be lower (p=0.039) than the non-responder group (2.2±0.7ng/mL). Furthermore, week 12 total testosterone plasma concentration in the responder group (1.8±1.3ng/mL) was found to be lower (p = 0.0097) than the non-responder group (3.8±0.7ng/mL); week 12 free testosterone plasma concentration in the responder group (6.4±4.8pg/mL) was found to be lower (p = 0.0054) than the non-responder group (14.4±2.7pg/mL). Finally, correlation analyses revealed a negative correlation between the reduction of ABC-I and week 12 total testosterone level (coefficient of determination R² = 0.40).

Conclusions: Preliminary analysis found that baseline PREG and 12-week testosterone (both free and total) levels were associated with reduction of ABC-I. These findings suggest that effectiveness of PREG might be related to testosterone blood levels and additional research is needed to replicate these findings in a controlled trial.