Over 25 selected naphthalenesulfonic acid derivatives were evaluated for their inhibitory effect on two different functional domains of the HIV-1 reverse transcriptase (RT), namely the ribonuclease H and DNA polymerase activities. Most of the analogues were found to be either specific toward the DNA polymerase activity or showed nonselective inhibition of both catalytic functions. The most active compounds are either symmetrical derivatives or nonsymmetrical derivatives containing a lipophilic appendage consisting of a palmitoyl or cholesteryl moiety. The six most active compounds in the preliminary screen, derivatives 6, 16, 17, 23, 26, and 27, were subjected to experiments to determine their 50% inhibitory concentration (IC50) values in the assays that measure RNA-dependent DNA polymerase (RDDP), DNA-dependent DNA polymerase (DDDP), and ribonuclease H (RNase H) functions of HIV-1 RT. The most potent derivative was a nonsymmetric cholesterol-linked 4-amino-5-hydroxy-2,7-naphthalenedisulfonic acid analogue, compound 23, which demonstrated an IC50 value of 0.06 microM for inhibiting RDDP activity. Inhibition of DDDP and RNase H activity for this compound was demonstrated at concentrations that were over 100-fold of that for inhibiting RDDP activity. However, the potency of this active compound does not correlate in the whole virus assay, probably due to a lack of cellular entry. The cholesterol derivative, 23, also possesses HIV-1 protease inhibitory activity and belongs to a unique class of multifunctional HIV-1 inhibitors.
Symmetric bis(naphthalenesulfonic acid) derivatives containing a variety of spacers have been synthesized and evaluated for anti-HIV-1 activity in four assay systems. In the assay that measured inhibition of HIV-1-induced cytopathogenicity using a laboratory strain (HTLV-IIIB), a hexamethylene and octamethylene spacer derivative of 4-amino-5-hydroxy-2,7-naphthalenedisulfonic acid emerged as the most potent derivatives. The hexamethylene spacer analog exhibited an in vitro therapeutic index that was > 120. Selected derivatives were tested in the giant cell formation assay. In this assay, the most potent derivative was, again, the hexamethylene compound. Evaluation of selected derivatives against a clinical isolate of HIV-1 (HE strain) revealed that the hexamethylene derivative was the most potent compound. In the assay that measured the inhibition of HIV-1-induced cytopathogenesis in human peripheral blood lymphocytes, the hexamethylene compound emerged as the most active derivative, demonstrating a 50% inhibitory concentration of 1.3 microM. These studies clearly demonstrate that certain naphthalenesulfonic acid moieties when coupled to specific spacers were synergistic in producing anti-HIV-1 activity at nontoxic concentrations. In the 4-amino-5-hydroxy-2,7-naphthalenedisulfonic acid series, shortening of the spacer length, preferably with a flexible polymethylene chain, was highly beneficial for increasing anti-HIV-1 potency.
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