Abstract.A so far unknown third polymorph (form III) of 5-amino-2,3-dihydro-1,4-phthalazinedione (luminolate) monosodium salt could be isolated phase pure and its structure was determined by powder X-ray diffraction and Rietveld refinement [cell parameters: a = 8.0364(2) Å, b = 3.69765(5) Å, c = 26.4246(7) Å, β = 96.346(2)°, V = 780.42(3) Å 3 , space group P2 1 /c]. The new structure shows many similarities to the structure of the known form II and the consequently slim differences in the diffraction traces could have easily been over-

At least since March 2020, the severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) pandemic and the multi-organ coronavirus disease 2019 (COVID-19) are keeping a firm grip on the world. Although most cases are mild, older patients and those with co-morbidities are at increased risk of developing a cytokine storm, characterized by a systemic inflammatory response leading to acute respiratory distress syndrome and organ failure. The present paper focuses on the small molecule MP1032, describes its mode of action, and gives rationale why it is a promising option for the prevention/treatment of the SARS-CoV-2-induced cytokine storm. MP1032 is a phase-pure anhydrous polymorph of 5-amino-2,3-dihydro-1,4-phthalazinedione sodium salt that exhibits good stability and bioavailability. The physiological action of MP1032 is based on a multi-target mechanism including localized, self-limiting reactive oxygen species (ROS) scavenging activities that were demonstrated in a model of lipopolysaccharide (LPS)-induced joint inflammation. Furthermore, its immune-regulatory and PARP-1-modulating properties, coupled with antiviral effects against SARS-CoV-2, have been demonstrated in various cell models. Preclinical efficacy was elucidated in LPS-induced endotoxemia, a model with heightened innate immune responses that shares many similarities to COVID-19. So far, during oral clinical development with three-month daily administrations, no serious adverse drug reactions occurred, highlighting the outstanding safety profile of MP1032.

At least since March 2020, the multiorgan disease COVID-19 has a firm grip on the world. Although most of the cases are mild, patients from risk populations could develop a cytokine storm, which is characterized by a systemic inflammatory response leading to acute respiratory distress syndrome and organ failure. The present paper will introduce the small molecule MP1032, describe its mode of action, and give rationale why it is a promising option for prevention/treatment of SARS-CoV-2-induced cytokine storm. MP1032 is a phase-pure anhydrous polymorph of 5-amino-2,3-dihydro-1,4-pthalazinedione sodium salt that exhibits good stability and bioavailability. The physiological action of MP1032 is based on a multi-target mechanism including localized, self- limiting antioxidant activities that were demonstrated in a model of lipopolysaccharide (LPS)-induced joint inflammation. Furthermore, immune-regulatory and PARP-1 modulating properties, coupled with antiviral effects against SARS-CoV-2 were shown in various cell models. Efficacy has been preclinically elucidated in LPS-induced endotoxemia, a model with excessively activated immune responses that shares many similarities to COVID-19. So far, during oral clinical development with three-months daily administrations, no serious adverse drug reactions occurred highlighting the outstanding safety profile of MP1032.

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