Physicochemical properties of a nonpeptide cyclic urea HIV protease inhibitor (DMP 323)

Abstract

DMP 323 ([4R-(4α, 5α, 6β, 7β)]-hexahydro-5,6-bis(hydroxy)-1,3-bis ([(4-hydroxymethyl)phenyl]methyl)-4,7-bis(phenylmethyl)-2H-1,3-diazepin-2-one), a potent inhibitor of HIV protease and HIV replication, is a white irregular-shaped nonhygroscopic crystalline material. Differential scanning calorimetry revealed a single melt peak at 195.7°C. DMP 323 was practically insoluble in water at 10 µg/ml (pH 8.1) at 25°C. The aqueous solubility was unaffected by changes in pH. The logarithm of the solubility of DMP 323 is a linear function of the percentage of water miscible cosolvents. The highest solubility values of DMP 323 were 272 mg/ml in 95% (v/v) ethanol in water, 160 mg/ml in propylene glycol, 144 mg/ml in polyethylene glycol 400, 65.5 mg/ml in 70% (w/w) polyethylene glycol 1450 in water, 64.2 mg/ml in polyoxyethylene sorbitan monooleate, and 1.61 mg/ml in glycerin. DMP 323 was stable as a function of pH with no loss observed at pH 3, 5, 7, 9 and 12.7 in aqueous buffers containing 5% (v/v) methanol after eight weeks at 40°C. In polyethylene glycol 400 solutions, the degradation of DMP 323 was approximated with apparent first order kinetics at elevated temperatures. Butylated hydroxytoluene and butylated hydroxyanisole were effective antioxidants in reducing the degradation in polyethylene glycol 400 solutions while citric acid afforded no protection from the degradation. Argon flushing was effective at reducing the oxidative degradation in polyethylene glycol 400 solutions stored at room temperature. Consistent with the oxidative degradation, DMP 323 degraded to the mono- and dibenzaldehyde, the monobenzoic acid, and the monobenzaldehyde monobenzoic acid derivatives.