SRF617 Is a Potent Inhibitor of CD39 with Immunomodulatory and Antitumor Properties.

CD39 (ENTPD1) is a key enzyme responsible for degradation of extracellular ATP and is upregulated in the tumor microenvironment (TME). Extracellular ATP accumulates in the TME from tissue damage and immunogenic cell death, potentially initiating proinflammatory responses that are reduced by the enzymatic activity of CD39. Degradation of ATP by CD39 and other ectonucleotidases (e.g., CD73) results in extracellular adenosine accumulation, constituting an important mechanism for tumor immune escape, angiogenesis induction, and metastasis. Thus, inhibiting CD39 enzymatic activity can inhibit tumor growth by converting a suppressive TME to a proinflammatory environment. SRF617 is an investigational, anti-CD39, fully human IgG4 Ab that binds to human CD39 with nanomolar affinity and potently inhibits its ATPase activity. In vitro functional assays using primary human immune cells demonstrate that inhibiting CD39 enhances T-cell proliferation, dendritic cell maturation/activation, and release of IL-1ß and IL-18 from macrophages. In vivo, SRF617 has significant single-agent antitumor activity in human cell line-derived xenograft models that express CD39. Pharmacodynamic studies demonstrate that target engagement of CD39 by SRF617 in the TME inhibits ATPase activity, inducing proinflammatory mechanistic changes in tumor-infiltrating leukocytes. Syngeneic tumor studies using human CD39 knock-in mice show that SRF617 can modulate CD39 levels on immune cells in vivo and can penetrate the TME of an orthotopic tumor, leading to increased CD8+ T-cell infiltration. Targeting CD39 is an attractive approach for treating cancer, and, as such, the properties of SRF617 make it an excellent drug development candidate.

Selective nitros(yl)ation induced in vivo by a nitric oxide-donating cyclooxygenase-2 inhibitor: a NObonomic analysis.

Nitric oxide (NO) enhances anti-inflammatory drug action. Through a metabonomics approach termed "NObonomics," the effects of a prototypic NO donor (organic nitrate)-cyclooxygenase-2 inhibitor hybrid (NO-coxib), NMI-1093, on the NO metabolite status of the circulation and major organs have been profiled in vivo in the rat. An oral anti-inflammatory NMI-1093 bolus elicited acute tissue-, time-, and dose-dependent changes in oxidative and nitroso/nitrosyl NO metabolites. Gastric N-nitrosation and hepatic S-nitrosation and heme nitrosylation emerged as sensitive indices of this NO-coxib's metabolism. Acute NMI-1093-induced nitros(yl)ation correlated positively as a function of nitrate plus nitrite formation across all organs examined, suggesting a unifying in vivo mechanism consequent to NMI-1093 biotransformation that links oxidative and nitros(yl)ative routes of NO chemical biology and thereby may support downstream NO signaling. NMI-1093 depressed erythrocyte nitros(yl)ation, likely by inhibiting cellular carbonic anhydrase and shifting the intracellular balance between nitrogen oxides and carbonates. Glutathione-S-transferase or cytochrome P450 inhibitors also attenuated NMI-1093's NO metabolism in a compartment-selective fashion. Although not itself a NO donor, the des-nitro coxib analog of NMI-1093 influenced basal NO metabolite profiles, implicating a cyclooxygenase-NO synthase interaction in physiological NO regulation. By detailing the global NO metrics of a unique coxib bearing a popular NO-donor pharmacophore (i.e., a nitrate moiety) and defining some critical mechanistic determinants, this study demonstrates how NObonomics can serve as valuable tool in helping elucidate NO systems biology and the effect of NO-donor and non-NO-donating therapeutics thereon.

Differential nitros(yl)ation of blood and tissue constituents during glyceryl trinitrate biotransformation in vivo.

Nitric oxide (NO)-derived products may modify tissue constituents, forming S- and N-nitroso adducts and metal nitrosyls implicated in NO signaling. Nitrovasodilator drugs have been in widespread use for more than a century, yet their biotransformation pathways to NO and their effects as NO donors across tissues remain ill defined. By using a metabonomics approach (termed "NObonomics") for detailing the global NO-related metabolism of the cornerstone nitrovasodilator, glyceryl trinitrate (GTN; 0.1-100 mg/kg), in the rat in vivo, we find that GTN biotransformation elicits extensive tissue nitros(yl)ation throughout all major organ systems. The corresponding reaction products remained detectable hours after administration, and vascular tissue was not a major nitros(yl)ation site. Extensive heart and liver modifications involved both S- and N-nitrosation, and RBC S-nitrosothiol formation emerged as a sensitive indicator of organic nitrate metabolism. The dynamics of GTN-derived oxidative NO metabolites in blood did not reflect the nitros(yl)ation patterns in the circulation or in tissues, casting doubt on the usefulness of plasma nitrite/nitrate as an index of NO/NO-donor biodynamics. Target-tissue NO metabolites varied in amount and type with GTN dose, suggesting a dose-sensitive shift in the prevailing routes of GTN biotransformation ("metabolic shunting") from thiol nitrosation to heme nitrosylation. We further demonstrate that GTN-induced nitros(yl)ation is modulated by a complex, tissue-selective interplay of enzyme-catalyzed pathways. These findings provide insight into the global in vivo metabolism of GTN at pharmacologically relevant doses and offer an additional experimental paradigm for the NObonomic analysis of NO-donor metabolism and signaling.