A series of triterpene compounds characterized by a stringent structure-activity relationship were identified as potent and selective inhibitors of human immunodeficiency virus type 1 (HIV-1) replication. Currently studied betulinic derivatives have 50% inhibitory concentrations (ICss) agaeHIV-1 strain III/LAI in the 10 nM range in several cellular infection assays but are inactive against HIV-2. These compounds did not significantly inhibit the in vitro activities of several purified HIV-l enzymes. Rather, they ap ed to block virus infection at a postbinding, envelope-dependent step involved in the fusion of the virus to the cell membrane. CCID5o) and cultured for 5 days. Cell viability was assessed by the spectrophotometric 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium-based assay (9). Mock-infected cultures were carried out in parallel to determine the degree of cytotoxicity of the compounds. p24 core antigen in culture supernatants was determined by ELISA (NEK060B kit from New England Nuclear). RT activity was measured by a poly(rA) 3H SPA scintillation proximity assay (NK9020 from Amersham). The antiviral assay using MT4 cells was as described (10). The effect of compounds on the kinetics of viral production in human peripheral blood mononuclear cells (PBMCs) was also assayed. PBMCs from seronegative donors were isolated by Ficoll/Hypaque (Pharmacia) and stimulated for 3 days with phytohemagglutinin (2.5 pg/ml; Difco). Cells were then washed three times with medium, pelleted, and incubated with 50-100 CCID50 of virus stock per ml. After 1 hr at room temperature, cells were resuspended in RPMI 1640 medium containing 10%6 fetal bovine serum, 10%6 T-cell growth factors (Lymphocult, Biotest Diagnostics, Danville, NJ), and anti-interferon a neutralizing antibody (Bayer, Wuppertal, F.R.G.) at 80 units/ml. Cells were plated at 106 per ml in six-well culture plates (Costar) in the presence of the compound to be tested. At 3, 7, 10, and 14 days after infection, cultures were harvested and viable cells were examined by trypan blue exclusion. Aliquots of supernatants were frozen at -700C until tested for p24 antigen, and cells were resuspended at the same density in complete fresh medium with the same concentration of the tested drug.Determination of Cytoplasmic Proviral DNA. Shortly after infection, the proviral DNA obtained from a selective extraction was quantified by PCR amplification. H9 cells were preincubated in the presence or absence of the drug to be tested for 1 hr, infected with HIV-1 (LAI) at 500 CCIDso/ml for 1 hr, and grown in culture medium for another hour. Cells were then washed intensively, and cytoplasmic proviral DNA was extracted by a digitonin/proteinase K/RNase Abbreviations: AZT, 3'-azido-3'-deoxythymidine; HIV, human immunodeficiency virus; PBMC, peripheral blood mononuclear cell; sCD4, soluble CD4; RT, reverse transcriptase. tTo whom reprint requests should be addressed. 3564The publication costs of this article were defrayed in part by page charge payment. This article mus...

SAR3419 is a novel anti-CD19 humanized monoclonal antibody conjugated to a maytansine derivate through a cleavable linker for the treatment of B-cell malignancies. SAR3419 combines the strengths of a high-potency tubulin inhibitor and the exquisite B-cell selectivity of an anti-CD19 antibody. The internalization and processing of SAR3419, following its binding at the surface of CD19-positive human lymphoma cell lines and xenograft models, release active metabolites that trigger cell-cycle arrest and apoptosis, leading to cell death and tumor regression. SAR3419 has also been shown to be active in different lymphoma xenograft models, including aggressive diffuse large B-cell lymphoma, resulting in complete regressions and tumor-free survival. In these models, the activity of SAR3419 compared favorably with rituximab and lymphoma standard of care chemotherapy. Two phase I trials with 2 different schedules of SAR3419 as a single agent were conducted in refractory/relapsed B-cell non-Hodgkin lymphoma. Activity was reported in both schedules, in heavily pretreated patients of both follicular and diffuse large B-cell lymphoma subtypes, with a notable lack of significant hematological toxicity, validating SAR3419 as an effective antibody-drug conjugate and opening opportunities in the future. Numerous B-cell-specific anti-CD19 biologics are available to treat B-cell non-Hodgkin lymphoma, and early phase I results obtained with SAR3419 suggest that it is a promising candidate for further development in this disease. In addition, thanks to the broad expression of CD19, SAR3419 may provide treatment options for B-cell leukemias that are often CD20-negative.

A novel series of omega-aminoalkanoic acid derivatives of betulinic acid were synthesized and evaluated for their activity against human immunodeficiency virus (HIV). The anti-HIV-1 activity of several members of this new series was found to be in the nanomolar range in CEM 4 and MT-4 cell cultures. The optimization of the omega-aminoalkanoic acid side chain is described. The presence of an amide function within the side chain was found important for optimal activity. RPR 103611 (14g), a statine derivative, was found to be inactive against HIV-1 protease, reverse transcriptase, and integrase as well as on gp120/CD4 binding. "Time of addition" experiments suggested interaction with an early step of HIV-1 replication. As syncytium formation, but not virus-cell binding, seems to be affected, betulinic acid derivatives are assumed to interact with the postbinding virus-cell fusion process.