Computational analysis of CYP3A4-mediated metabolism to investigate drug interactions between anti-TB and anti-HIV drugs in HIV/TB co-infection

The treatment of human immunodeficiency virus (HIV)-related tuberculosis (TB) includes combination therapy, in which antiretroviral drugs and anti-TB drugs are co-administered. The complexities associated with the treatment of dual infection by Mycobacterium tuberculosis and HIV include occurrence of drug–drug interactions, in addition to pill burden, overlapping drug toxicity, and immune reconstitution inflammatory syndrome. Drug–drug interactions can occur between these drugs toward cytochrome P450 3A4 (CYP3A4), a drug-metabolizing enzyme. A thorough understanding of these interactions can prevent occurrence of treatment failures and drug toxicity. Molecular docking studies were carried out for FDA-approved drugs, to predict binding mechanism of anti-TB drugs with CYP3A4 and to compare them with our previous studies on antiretroviral drugs, in order to infer possible occurrence of drug–drug interactions. The core regimen of anti-TB treatment viz., rifampin (RIF), isoniazid (INH), and pyrazinamide (PZA) showed similar binding mode (i.e., competitive binding) via utilizing the same binding residue, Arg212 in CYP3A4. This regimen also shared similar binding mode with antiretroviral protease inhibitors except tipranavir, nelfinavir, lopinavir, and atazanavir. Contraindicated drug interactions were not observed between non-nucleoside reverse transcriptase inhibitors, delavirdine, efavirenz, and etravirine; and anti-TB drugs, RIF, INH, and PZA. The contraindications occurring within anti-TB drugs can be negated with inhibitory effect of INH to induction effect of RIF toward CYP3A4. We evaluated the importance of Arg212 along with Ser119, Ala370, Arg372, and heme moiety for mediating oxidative metabolism of drugs. These drug interaction details were incorporated into our web server by creating a database called “CYP3A4 DDIDB” and it is open accessible from http://cyp.bicpu.edu.in.