Darunavir

Darunavir (Prezista) is a drug used to treat HIV infection. It is in the protease inhibitor class. Developed by pharmaceutical company Tibotec, darunavir is named after Arun K. Ghosh, the chemist who discovered the molecule at the University of Illinois in Chicago. It was approved by the Food and Drug Administration (FDA) on June 23, 2006.^[1]

Darunavir is a second-generation protease inhibitor (PIs), designed specifically to overcome problems with the older agents in this class, such as indinavir. Early PIs often have severe side effects and drug toxicities, require a high therapeutic dose, are costly to manufacture, and show a disturbing susceptibility to drug resistant mutations. Such mutations can develop in as little as a year of use, and effectively render the drugs useless.

Darunavir was designed to form robust interactions with the protease enzyme from many strains of HIV, including strains from treatment-experienced patients with multiple resistance mutations to PIs.^[2][3]

Darunavir received much attention at the time of its release, as it represents an important treatment option for patients with drug-resistant HIV. Patient advocacy groups pressured developer Tibotec not to follow the previous trend of releasing new drugs at prices higher than existing drugs in the same class. Darunavir was priced to match other common PIs already in use, such as kaletra. The drug is still costly, at around $9000 for a one year supply.^[4][5][6]

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Efficacy

Darunavir showed superiority to lopinavir and other protease inhibitors in the POWER trials. The POWER 1 and POWER 2 are designed for treatment-experienced patients, together with supportive data from the POWER 3 analysis ^[7]. The patients eligible for these studies had experience with at least one protease inhibitor, one non-nucleoside reverse transcriptase inhibitor (NNRTI) and two nucleoside reverse transcriptase inhibitors (NRTI), and had one or more primary protease inhibitor mutations.

Darunavir also showed superior results to lopinavir in the TITAN trials (pre-planned, secondary endpoint, week 48), which was designed for patients with less advanced HIV disease compared to the POWER trials^[8].

TITAN trial

Analysis of 595 treatment-experienced patients being lopinavir/r-naïve, HIV-1 infected adults with a viral load of >1000 HIV-1 RNA copies/mL. Pre-planned secondary endpoint findings include:

• 71 percent of patients in the darunavir/r arm reached an undetectable viral load (<50 copies/mL) vs. 60 percent of patients in the lopinavir/r arm, a statistically significant difference (p=0.005)
• 77 percent of patients in the darunavir/r arm achieved at least a 1 log10 reduction in HIV RNA vs. 69 percent in the lopinavir/r arm, a statistically significant difference (p=0.028)
• The median increase from baseline in CD4 cell count was similar between the darunavir/r and lopinavir/r arms (88 cells per cubic millimeter vs. 81 cells per cubic millimeter)

Development of resistance also was studied. Findings include:

• 10 percent of patients in the darunavir/r arm experienced virological failure vs. 22 percent of patients in the lopinavir/r arm
• Among patients experiencing virologic failure who had baseline and endpoint genotype data, 21 percent of patients in the darunavir/r arm developed primary PI resistance mutations vs. 36 percent of patients in the lopinavir/r arm, and 14 percent of patients in the darunavir/r arm developed primary NRTI resistance mutations vs. 27 percent of patients in the lopinavir/r arm

POWER 1 and POWER 2 trials

A pooled analysis of results from POWER 1 and POWER 2 demonstrated that after 24 weeks:

• Significantly more treatment-experienced patients achieved a reduction in viral load at the 24-week primary endpoint with DARUNAVIR, compared with the investigator-selected PI (70% vs 21%, respectively).
• Almost four times as many treatment-experienced patients (45%) have achieved an undetectable viral load with the DARUNAVIR containing regimen, compared with the investigator-selected PI arm (12%).
• In treatment-experienced patients, the DARUNAVIR containing regimen increases CD4 cell counts five times more than the investigator-selected PI arm (92 cells/mm3 vs 17 cells/mm3, respectively) (Johnson & Johnson Press Release, 2006; Lazzarin, 2005)

The efficacy results of POWER 1 and POWER 2 are confirmed by data from a large, non-randomized, open-label analysis known as POWER 3. After 24 weeks:

• 65 percent of patients achieved a reduction in viral load of 1 log10 or more, versus baseline.
• 40 percent of patients reached undetectable virus levels (<50 HIV RNA copies/mL). (Molina, 2005)

Safety

As other antivirals, DARUNAVIR does not cure HIV infection or AIDS, and does not prevent passing HIV to others.

In studies, DARUNAVIR was generally well tolerated. Mild to moderate rash was seen in 7% of patients. Some patients developed severe rash. In clinical studies, 0.3% of patients discontinued due to rash. The most common moderate to severe side effects associated with DARUNAVIR include diarrhea (2.3%), headache (3.8%), abdominal pain (2.3%), constipation (2.3%), and vomiting (1.5%). Four percent of patients discontinued treatment due to adverse events. People who are allergic to DARUNAVIR or any of its ingredients, or ritonavir (NORVIR) should not take DARUNAVIR.

There were few relevant drug-drug interactions with other medications commonly used in HIV patient populations, such as other antiretroviral medications, proton pump inhibitors, and H2 receptor antagonists. Patients should talk to their healthcare provider about all the medicines they are taking or plan to take, including prescription and nonprescription medicines, vitamins, and herbal supplements.

Before taking DARUNAVIR, patients should tell their healthcare provider if they have any medical conditions, including diabetes, liver problems, hemophilia, or allergy to sulfa medicines and should tell their doctor if they are pregnant or planning to become pregnant, or are nursing. DARUNAVIR should be used with caution in patients with hepatic impairment.

High blood sugar, diabetes or worsening of diabetes, muscle pain, tenderness or weakness, and increased bleeding in people with hemophilia have been reported in patients taking protease inhibitor medicines like DARUNAVIR ™ . Changes in body fat have been seen in some patients taking anti-HIV medicines, including loss of fat from legs, arms and face, increased fat in the abdomen and other internal organs, breast enlargement and fatty lumps on the back of the neck. The cause and long-term health effects of these conditions are not known at this time.

Clinical laboratory safety observed in the DARUNAVIR group was comparable to the control group. (Product Monograph, Darunavir)

Dosing and Administration

The recommended oral dose of DARUNAVIR tablets is 600 mg (two 300 mg tablets) twice daily (BID) taken with ritonavir 100mg BID and with food. The drug can be taken with any type of food.

Additional Studies Involving DARUNAVIR

• TMC114-C211: Investigating a dose of 800 mg of the drug boosted with 100 mg of ritonavir once daily in treatment-naïve patients.
• TMC114-C214: Investigating a dose of 600 mg of the drug boosted with 100 mg of ritonavir twice daily in moderately treatment-experienced patients.
• DUET trial: The drug is being studied with TMC125, an investigational non-nucleoside reverse transcriptase inhibitor, in one of the few HIV clinical trials to involve two investigational HIV treatments in treatment-experienced patients. (Tibotec 2006)

References

• Lazzarin A, Queiroz-Telles F, Frank I, Rockstroh J, Walmsley S, De Paepe E, Vangeneugden T, Spinosa-Guzman S and Lefebvre E Lazzarin A, et al. XVI IAC 2006.
• Johnson & Johnson FDA Approval Press Release, June 23 2006, http://www.jnj.com/news/jnj_news/20060623_191250.htm;jsessionid=NT1BC4RC4RHKYCQPCAOWU3YKB2IIWTT
• Molina JM, Cohen C, Katlama C et al. TMC114/r in treatment-experienced HIV patients in power 3: 24-week efficacy and safety analysis. Poster abstract TUPE0060.
• Janssen-Ortho, Darunavir Mongraph information. Updated 2006. http://www.janssen-ortho.com/JOI/pdf_files/Darunavir_E.pdf
• TMC114, Tibotec, http://www.tibotec.com/bgdisplay.jhtml?itemname=HIV_tmc114
• Ghosh, A. K., et al. Bioorg. Med. Chem. Lett. 1998, 8, 687-90;
• Mitsuya, H. Ghosh, A. K., et al. J. Virology 2002, 76, 1349;
• Ghosh, A. K. Duzguiness, N., et al. Antiviral Res. 2002, 54, 29;
• Koh, Y., Ghosh, A. K., Mitsuya, H., et al. Antimicrobial Agents and Chemotherapy, 2003, 47, 3123
• Ghosh, A. K., Mitsuya, H., et al. ChemMedChem 2006, 1, 937
• A. K. Ghosh, B. D. Chapsal, I. T. Weber, H. Mitsuya. Acc. Chem. Res. 2007, ASAP.
• A. K. Ghosh, Z. L. Dawson, H. Mitsuya. Bioorg. Med. Chem. 2007, 15, 7576.

See also

• Tibotec