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The sprouting of new blood vessels, or angiogenesis, is necessary for any solid tumor to grow large enough to cause life-threatening disease. Vascular endothelial growth factor (VEGF) is one of the key promoters of tumor induced angiogenesis. VEGF receptors, the tyrosine kinases Flt-1 and KDR, are expressed on vascular endothelial cells and initiate angiogenesis upon activation by VEGF. 1-Anilino-(4-pyridylmethyl)-phthalazines, such as CGP 79787D (or PTK787 / ZK222584), reversibly inhibit Flt-1 and KDR with IC50 values < 0.1 μM. CGP 79787D also blocks the VEGF-induced receptor autophosphorylation in CHO cells ectopically expressing the KDR receptor (ED50 = 34 nM). Modification of the 1-anilino moiety afforded derivatives with higher selectivity for the VEGF receptor tyrosine kinases Flt-1 and KDR compared to the related receptor tyrosine kinases PDGF-R and c-Kit. Since these 1-anilino-(4-pyridylmethyl)phthalazines are orally well absorbed, these compounds qualify for further profiling and as candidates for clinical evaluation.

The reactions of a variety of trico-ordinate phosphorus compounds, ArnP(OR)3-n (n = 1 or 2), and cyclic analogues, with acrylonitrile, ethyl acrylate or ethyl phenylpropiolate and alcohols or phenols in low polarity media gives rise to a wide range of pentaco-ordinate phosphorus compounds. Attempts to extend this synthetic route to phosphoranes containing P-N or P-S bonds met with no success.

A series of aza-peptide analogs with a (hydroxyethyl)hydrazine isostere has been synthesized as HIV-1 protease inhibitors using a simple synthetic scheme. Structure−activity studies based on the X-ray of a previously described inhibitor−enzyme complex led to potent inhibitors with antiviral activity in the low-nanomolar range. The S-configuration of the transition-state hydroxyl group was preferred in this series. Small modifications of the P2P3 and P2‘P3‘ substituents had little effect on enzyme inhibition but greatly influenced the pharmacokinetic profile. As a result of these studies, the symmetrically acylated compound 8a and its close analog 24a bearing a methyl carbamate in P3 and an ethyl carbamate in P3‘ position were identified as potent inhibitors with plasma concentrations exceeding antiviral ED50 values 150-fold following oral application in mice.

On the basis of previously described X-ray studies of an enzyme/aza-dipeptide complex,⁸ aza-dipeptide analogues carrying N-(bis-aryl-methyl) substituents on the (hydroxethyl)hydrazine moiety have been designed and synthesized as HIV-1 protease inhibitors. By using either equally (12) or orthogonally (13) protected dipeptide isosteres, symmetrically and asymmetrically acylated aza-dipeptides can be synthesized. This approach led to the discovery of very potent inhibitors with antiviral activities (ED50) in the subnanomolar range. Acylation of the (hydroxethyl)hydrazine dipeptide isostere with the l-tert-leucine derivative 29 increased the oral bioavailability significantly when compared to the corresponding l-valine or l-isoleucine derivatives. The bis(l-tert-leucine) derivatives CGP 75355, CGP 73547, CGP 75136, and CGP 75176 combine excellent antiviral activity with high blood concentration after oral administration. Furthermore, they show no cross-resistance with saquinavir-resistant strains and maintain activity against indinavir-resistant ones. Consequently they qualify for further profiling as potential clinical candidates.

The murine model of acquired immunodeficiency disease was used to evaluate both the antiretroviral and antiherpetic activities of the acyclic nucleotide analog 9-(2-phosphonylmethoxyethyl)adenine (PMEA). The antiretroviral activity of PMEA was compared with that of azidothymidine (AZT) in mice receiving the drug either immediately after infection or at late times in disease progression. Both AZT (oral, 30 mg/kg) and PMEA (parenteral, 25 and 5 mg/kg) were effective in slowing the development of disease when administered daily beginning on the day of infection. In contrast, neither drug alone was effective in modifying disease outcome when administered several weeks after viral infection. Human recombinant alpha interferon (rhuIFN alpha-B/D at 5 x 10(7) U/kg) was also ineffective when administered late in the course of disease. However, when administered in combination, both alpha interferon and PMEA (25 mg/kg) were able to suppress disease progression even when treatment was initiated as late as 3 weeks postinfection. Mice that were immunocompromised due to LP-BM5 virus infection were highly susceptible to acute (lethal) infection with herpes simplex virus type 1, whereas their immunocompetent littermates were not. PMEA was as effective as acyclovir in the treatment of opportunistic herpes simplex virus type 1 infections in LP-BM5 virus-infected mice. Thus, like AZT, PMEA was effective against retrovirus infection, and, like acyclovir, PMEA was effective against herpes simplex virus type 1 infection. This gives PMEA the unique potential of being useful in the treatment of opportunistic herpes simplex virus infections as well as the underlying retroviral disease.

The lytic and bactericidal actions of polymyxin B on whole cells and spheroplasts of Pseudomonas aeruginosavaried markedly with the suspending media, and there was little correlation between them. Relative rates of lysis of these preparations and also of Bacillus megateriumprotoplasts suggested that polymyxin causes progressive damage to the cytoplasmic membrane, such that membrane permeability towards various ions increased as follows: K+> Na+> NO3−> Cl−, Ca2+, H2PO4−/HPO42−. Impermeant compounds, such as NaCl and sucrose, protected whole cells against lysis but not against death. It is suggested that lysis of whole cells by polymyxin is a secondary effect, resulting from entry of solutes normally excluded by the cytoplasmic membrane and the fragility of the damaged outer membrane. Because the degree of lysis varies with the external solutes, it should be treated with caution as a descriptor of polymyxin activity.

The bactericidal activity of 23 beta-lactam antibiotics was compared in slowly growing bacteria cultured in a chemostat. In an attempt to mimic possible in vivo conditions, slowly growing cultures were produced by limitation of iron, glucose, phosphate, or magnesium. Only select antibiotics remained effectively bactericidal against slowly growing cells. For these compounds, the rate of antibiotic-induced loss of viability was a constant when killing was expressed per generation (in contrast to absolute time) in that slowly growing bacteria were killed proportionately more slowly. Individual antibiotics differed greatly, however, in their specific bactericidal activities against slowly growing cells, i.e., in the absolute degree of killing elicited during exposure of the bacteria to MIC equivalents of the drugs. Specific bactericidal activities varied not only with drug structure but also with the bacterial strains and, to a lesser extent, with the nature of the growth-limiting nutrient. In slowly growing cultures exposure to the low drug concentrations studied here (near MIC) caused killing without detectable lysis. Antibiotics with high specific bactericidal activities were capable of rapidly killing cultures of slowly growing pathogens despite extremely long generation times approaching those reported for in vivo growth rates.