Nevirapine

Discovery:

            Nevirapine falls into the drug family of HIV-1 reverse transcriptase inhibitors. This class of drug prevents the spread of infection by blocking the activity of reverse transcriptase (RT). RT is the enzyme responsible for transcribing the viral RNA into DNA which is then inserted into the genome of the infected host cell, allowing for proliferation of the infection. ^[1]

            The predecessor of this drug, Zidovudine, which was approved by the FDA in 1987, has a number of limitations. ^[1] The largest downfall is due to it lacking selectivity for RT as it has been shown to block DNA polymerase enzymes in mammals. This can lead to numerous problems, including but not limited to, bone marrow suppression, anemia, and pancreatitis. The requirements for a successor would include selectivity for RT, metabolically stable, and be able to cross the blood brain barrier as HIV-1 infects the central nervous system. ^[2]

            Karl D. Hargrave led the research at Boehringer Ingelheim Pharmaceuticals in an effort to discover such a suitable replacement. Without a structural basis on which to perform rational drug design, the researchers resorted to screening a group of compounds looking for activity. After discovering three series which showed promise, they conducted extensive structure activity relationship studies to find a compound which showed a good balance between bioavailability, solubility, metabolic stability, and selectivity in order to have a candidate for clinical trials. ^[2] Nevirapine, this candidate, was approved by the FDA in 1996. ^[1]

            While Hargrave and his team succeeded in avoiding the issues Zidovudine caused due to its poor selectivity, Nevirapine is not without unwanted effects. The most common side effect is the development of a mild to moderate rash which occurs in 13% of patients taking Nevirapine. The FDA also issued a warning about the potential for severe or life-threatening liver toxicity in 2000. Liver toxicity issues has been correlated to patients with high CD4 cell counts so avoiding the use of Nevirapine in these patients can help mitigate some of the issues. Despite these negative effects, Nevirapine’s usage has greatly reduced mortality from AIDS and is still widely used. ^[3]

Commercialization:

            Nevirapine, under the brand name Viramune, was first approved by the FDA on June 21^st, 1996. ^[4] The drug is manufactured by Boehringer Ingelheim, a large pharmaceutical company headquartered in Germany. ^[5] In 2017, Boehringer Ingelheim had €18.1 billion in net sales and spent €3.1 billion on research and development. ^[7]

The patent for the original formulation of nevirapine was filed January 12, 1995 and has since expired. ^[6] In 2005, the first generic tablets of nevirapine were approved by the FDA and are manufactured by the companies Ranbaxy Laboratories Limited and Aurobindo Pharma Limited, both of which are based in India. ^[10] On June 4^th, 2008, Boehringer Ingelheim filed a patent for an extended release formulation of nevirapine with the brand name Viramune XR. ^[8] This extended release 400mg tablet was approved by the FDA in 2011. ^[9] There is not a generic version of Viramune XR available as exclusivity rights from the patent have not expired yet. ^[8]

Nevirapine is no longer preferred as a first-line treatment for HIV-1 due to high incidences of liver toxicity. Increased risk factors for liver toxicity as an adverse effect includes higher CD4 counts as well as the female gender. Skin reactions are also common when taking nevirapine and can be severe or even life-threatening. ^[11] For these two reasons, the FDA issued a warning about the use of Nevirapine and recommends close monitoring for the first 18 weeks of treatment. ^[6]

Works Cited

1. Béthune, Marie-Pierre De. “Non-Nucleoside Reverse Transcriptase Inhibitors (NNRTIs), Their Discovery, Development, and Use in the Treatment of HIV-1 Infection: A Review of the Last 20 Years (1989–2009).” Antiviral Research, vol. 85, no. 1, 2010, pp. 75–90., doi:10.1016/j.antiviral.2009.09.008.

2. Hargrave, K D, et al. “Novel Non-Nucleoside Inhibitors of HIV-1 Reverse Transcriptase. 1. Tricyclic Pyridobenzo- and Dipyridodiazepinones.” Journal of Medicinal Chemistry, vol. 34, no. 7, 1991, p. 2231., doi:10.1021/jm00111a045.

3. Office, Editorial. "FDA Public Advisory for Nevirapine (Viramune)." Southern African Journal of HIV Medicine [Online], 6.1 (2005): 10. Web. 24 Sep. 2018

4. Office of the Commissioner. “HIV/AIDS History of Approvals - HIV/AIDS Historical Time Line 1995-1999.” U S Food and Drug Administration Home Page, Office of the Commissioner, www.fda.gov/ForPatients/Illness/HIVAIDS/History/ucm151079.htm.

5. “Our Company.” Boehringer-Ingelheim.com, www.boehringer-ingelheim.com/who-we-are/our-company.

6. Schneider, Heinrich, and Albrecht Christmann. Process for Preparing Nevirapine. 29 Oct. 1996.

7. “2017 Annual Report.” Boehringer Ingelheim, annualreport.boehringer-ingelheim.com/fileadmin/user_upload/BI_Annual_Report_2017_EN.pdf.

8. Cappola, Michael, and Svetlana Sienkiewicz. Extended Release Formulation of Nevirapine. 18 Dec. 2008.

9. Office of the Commissioner. “HIV/AIDS History of Approvals - HIV/AIDS Historical Time Line 2010 - 2017.” U S Food and Drug Administration Home Page, Office of the Commissioner, www.fda.gov/ForPatients/Illness/HIVAIDS/History/ucm279695.htm.

10. “U.S. Food and Drug Administration; FDA Tentatively Approves First Generic Nevirapine.” Food & Drug Law Weekly, Atlanta, 2005, p. 77.

11. Viramune (nevirapine) tablets; Viramune (nevirapine) oral suspension prescribing information Archived 2006-11-12 at the Wayback Machine.