Abstract Pediatric brain tumor is the leading cause of cancer-related deaths in pediatric patients ranging 0-19 years of age. Medulloblastoma is one of the most commonly occurring brain tumor in children. Sonic hedgehog (Shh) activated subgroup of medulloblastoma is considered to be highly aggressive and metastatic in nature. Recent studies and oncomine, a cancer microarray database has shown that GABAA receptor is down regulated in pediatric medulloblastoma. In this study, we have evaluated the anti-cancer effects of an anthelminthic drug ‘moxidectin' a GABAA receptor agonist. Treatment of medulloblastoma cells with moxidectin, resulted in reduced Protein kinase A (PKA) activity. Leading to the inhibition of Gli1, a major transcription factor of non-canonical Shh signaling. Moxidectin has inhibited the proliferation of Daoy, UW426, UW228, ONS76, and PFSK1 medulloblastoma cells and significantly induced apoptosis in a concentration and time dependent manner in all the cell lines. Western blotting and immunofluorescence microscopy demonstrated that moxidectin treatment significantly induced GABAA receptor expression and inhibited cAMP mediated PKA signaling. As a result, the non-canonical activation of Gli1 and its downstream effector molecules such as Pax-6, Oct-4, Sox-2 and Nanog were also inhibited by moxidectin treatment. Efficacy of moxidectin was also evaluated in subcutaneous and intracranial medulloblastoma tumor models. Our results demonstrated that daily oral administration of 2.5 mg/kg moxidectin suppressed the growth of medulloblastoma tumors by 55-70% in subcutaneous and intracranial models. Ex-vivo analysis of tumors by western blotting, IHC, TUNEL and H&E staining revealed that moxidectin suppressed medulloblastoma tumor progression by inhibiting PKA/Gli1 signaling axis indicating the significance of this pathway in medulloblastoma progression. To our knowledge, this study for the first time focuses on GABAA receptor agonist mediated PKA/Gli1 signaling inhibition. Most importantly, moxidectin is an FDA approved drug and is already in clinical use for the treatment of river blindness in humans with an established safety record, therefore any positive findings from our studies will prompt further clinical investigation into repositioning moxidectin for the treatment of MB patients. Citation Format: Itishree Kaushik, Sanjay Srivastava. PKA signaling: a friend or foe to pediatric medulloblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB254.