Gilead's Once-Daily Novel Prodrug for the Treatment of HIV Meets 24-Week Primary Objective in Phase 2 Study

-- Data Support Tenofovir Alafenamide Fumarate as Component of Future Single Tablet HIV Regimens --

 

FOSTER CITY, Calif.--(BUSINESS WIRE)--Oct 31, 2012 - Gilead Sciences, Inc. (Nasdaq: GILD) today announced that a Phase 2 clinical trial evaluating tenofovir alafenamide fumarate (TAF; formerly referred to as GS-7340), an investigational novel prodrug of tenofovir for the treatment of HIV-1 infection, met its primary objective. The ongoing study compares a once-daily single tablet regimen containing TAF 10 mg/elvitegravir 150 mg/cobicistat 150 mg/emtricitabine 200 mg with StribildTM (elvitegravir 150 mg/cobicistat 150 mg/emtricitabine 200 mg/tenofovir disoproxil fumarate 300 mg) among treatment-naïve adults. The TAF-based regimen achieved a similar virologic response to Stribild based on the proportion of patients with HIV RNA levels (viral load) of less than 50 copies/mL at 24 weeks of therapy (87 percent versus 90 percent, respectively).

Compared to Stribild, the TAF-based regimen demonstrated statistically significantly smaller reductions from baseline to week 24 in bone mineral density at the lumbar spine and hip (p<0.005). In addition, small, statistically significant differences were seen in serum creatinine and in calculated creatinine clearance between the two arms in favor of the TAF-containing regimen (p<0.02). No patient discontinued study drug for renal adverse events. There were no statistically significant differences in the frequency of laboratory abnormalities and the frequency and nature of adverse events were generally similar between the two arms. Both regimens were generally well tolerated. Gilead plans to submit these data for presentation at a scientific conference next year.

“These interim findings are encouraging and warrant advancing this TAF-containing single tablet regimen into Phase 3 development,” said Norbert Bischofberger, PhD, Executive Vice President, Research and Development and Chief Scientific Officer, Gilead Sciences.

TAF is also being studied in a second ongoing Phase 2 trial evaluating a single tablet regimen containing TAF, Janssen R&D Ireland's protease inhibitor Prezista® (darunavir), cobicistat and emtricitabine compared to Truvada® (emtricitabine and tenofovir disoproxil fumarate) plus Prezista and cobicistat, dosed as individual components. The study is fully enrolled and 24-week results will be available in the first half of 2013.

About the Study

The Phase 2 study is a randomized, double-blind 48-week clinical trial among HIV-1 infected adults with HIV RNA levels (viral load) greater than or equal to 5,000 copies/mL and CD4 cell counts greater than 50 cells/mm3. A total of 170 patients were randomized (2:1) to receive a once-daily tablet containing TAF 10 mg/elvitegravir 150 mg/cobicistat 150 mg/emtricitabine 200 mg (n=112) or Stribild (n=58). Bone mineral density was assessed in all patients by DEXA scans at baseline and at week 24.

The study is ongoing. Secondary endpoints will include the proportion of patients who achieve viral load of less than 50 copies/mL at 48 weeks of therapy, and changes in HIV-1 RNA and in CD4 cell count from baseline to Weeks 24 and 48. After week 48, patients will continue to take their blinded study drug until treatment assignments have been unblinded, at which point all will be given the option to participate in an open-label rollover extension and receive the TAF-based single tablet regimen.

Additional information about the study can be found at www.clinicaltrials.gov.

About Tenofovir Alafenamide Fumarate

Tenofovir alafenamide fumarate (TAF) is a nucleotide reverse transcriptase inhibitor and a novel prodrug of tenofovir, the active agent in Viread® (tenofovir disoproxil fumarate). Phase 1b dose-ranging studies identified a dose of TAF that is ten times lower than Viread and provides greater antiviral efficacy. The smaller milligram size of TAF may enable the development of new fixed-dose combinations and single tablet regimens for HIV therapy that are not feasible with Viread.

About Elvitegravir

As an integrase inhibitor, elvitegravir interferes with HIV replication by blocking the ability of the virus to integrate into the genetic material of human cells. Elvitegravir was licensed by Gilead from Japan Tobacco Inc. (JT) in March 2005. Under the terms of Gilead's agreement with JT, Gilead has exclusive rights to develop and commercialize elvitegravir in all countries of the world, excluding Japan, where JT retains rights. Gilead submitted a New Drug Application (NDA) to FDA for elvitegravir on June 27, 2012, and the agency has set a target action date under the Prescription Drug User Fee Act (PDUFA) of April 27, 2013.

About Cobicistat

Cobicistat is Gilead's proprietary potent mechanism-based inhibitor of cytochrome P450 3A (CYP3A), an enzyme that metabolizes drugs in the body. Unlike ritonavir, cobicistat acts only as a pharmacoenhancing or “boosting” agent and has no antiviral activity. Gilead submitted an NDA to FDA for cobicistat on June 28, 2012, and a PDUFA date of April 28, 2013 has been set.

TAF, elvitegravir and cobicistat are investigational products and their safety and efficacy have not yet been established.

Important Safety Information about Stribild

Stribild contains four Gilead compounds in a complete once-daily, single tablet regimen: elvitegravir 150 mg; cobicistat 150 mg; emtricitabine 200 mg; and tenofovir disoproxil fumarate 300 mg. Stribild is indicated as a complete regimen for the treatment of HIV-1 infection in adults who are antiretroviral treatment-naïve. Stribild does not cure HIV-1 infection.

BOXED WARNING: LACTIC ACIDOSIS/SEVERE HEPATOMEGALY WITH STEATOSIS and POST TREATMENT ACUTE EXACERBATION OF HEPATITIS B

 

  • Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs, including tenofovir disoproxil fumarate (“tenofovir DF”), a component of Stribild, in combination with other antiretrovirals.
  • Stribild is not approved for the treatment of chronic hepatitis B virus (HBV) infection and the safety and efficacy of Stribild have not been established in patients coinfected with HBV and HIV-1. Severe acute exacerbations of hepatitis B have been reported in patients who are coinfected with HBV and HIV-1 and have discontinued Emtriva or Viread, which are components of Stribild. Hepatic function should be monitored closely with both clinical and laboratory follow-up for at least several months in patients who are coinfected with HIV-1 and HBV and discontinue Stribild. If appropriate, initiation of anti-hepatitis B therapy may be warranted.

Contraindications

 

  • Coadministration: Do not use with drugs highly dependent on CYP3A for clearance and for which elevated plasma concentrations are associated with serious and/or life-threatening events. Do not use with drugs that strongly induce CYP3A as this may lead to a loss of virologic response and possible resistance to Stribild. Use with the following drugs is contraindicated: alfuzosin, rifampin, dihydroergotamine, ergotamine, methylergonovine, cisapride, lovastatin, simvastatin, pimozide, sildenafil for pulmonary arterial hypertension, triazolam, oral midazolam, and St. John's wort.

Warnings and Precautions

 

  • New onset or worsening renal impairment: Cases of acute renal failure and Fanconi syndrome have been reported with the use of tenofovir DF and Stribild. Monitor estimated creatinine clearance (CrCl), urine glucose, and urine protein in all patients prior to initiating and during therapy; additionally monitor serum phosphorus in patients with or at risk for renal impairment. Cobicistat may cause modest increases in serum creatinine and modest declines in CrCl without affecting renal glomerular function; patients with an increase in serum creatinine greater than 0.4 mg/dL from baseline should be closely monitored for renal safety. Do not initiate Stribild in patients with CrCl below 70 mL/min. Discontinue Stribild if CrCl declines below 50 mL/min. Avoid concurrent or recent use with a nephrotoxic agent.
  • Use with other antiretroviral products: Stribild should not be coadministered with products containing any of the same active components; with products containing lamivudine; with adefovir dipivoxil; or with products containing ritonavir.
  • Decreases in bone mineral density (BMD) and cases of osteomalacia have been seen in patients treated with tenofovir DF. Consider monitoring BMD in patients with a history of pathologic fracture or risk factors for bone loss.
  • Fat redistribution and accumulation have been observed in patients receiving antiretroviral therapy.
  • Immune reconstitution syndrome, including the occurrence of autoimmune disorders with variable time to onset, has been reported.

Adverse Reactions

 

  • Common adverse drug reactions in clinical studies (incidence greater than or equal to 5%; all grades) were nausea, diarrhea, abnormal dreams, headache and fatigue.

Drug Interactions

 

  • CYP3A substrates: Stribild can alter the concentration of drugs metabolized by CYP3A or CYP2D6.

Do not use with drugs highly dependent on these factors for clearance and for which elevated plasma concentrations are associated with serious and/or life-threatening adverse events.

 

  • CYP3A inducers: Drugs that induce CYP3A can decrease the concentrations of components of Stribild. Do not use with drugs that strongly induce CYP3A as this may lead to loss of virologic response and possible resistance to Stribild.
  • Antacids: Separate Stribild and antacid administration by at least 2 hours.
  • Prescribing information: Consult the full prescribing information for Stribild for more information on potentially significant drug interactions, including clinical comments.

Dosage and Administration

 

  • Adult dosage: One tablet taken orally once daily with food.
  • Renal impairment: Do not initiate in patients with CrCl below 70 mL/min. Discontinue in patients with CrCl below 50 mL/min.
  • Hepatic impairment: Not recommended in patients with severe hepatic impairment.

Pregnancy and Breastfeeding

 

  • Pregnancy Category B: There are no adequate and well-controlled studies in pregnant women. Use during pregnancy only if the potential benefit justifies the potential risk. An Antiretroviral Pregnancy Registry has been established.
  • Breastfeeding: Emtricitabine and tenofovir have been detected in human milk. Because of both the potential for HIV transmission and the potential for serious adverse reactions in nursing infants, mothers should be instructed not to breastfeed.

About Gilead Sciences

Gilead Sciences is a biopharmaceutical company that discovers, develops and commercializes innovative therapeutics in areas of unmet medical need. The company's mission is to advance the care of patients suffering from life-threatening diseases worldwide. Headquartered in Foster City, California, Gilead has operations in North America, Europe and Asia Pacific.

Forward-Looking Statement

This press release includes forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995 that are subject to risks, uncertainties and other factors, including risks related to the possibility of unfavorable 48-week results from this or other clinical trials involving TAF, including the trial evaluating the single tablet regimen of TAF, darunavir, cobicistat and emtricitabine. Further, Gilead may be unable to obtain clinical trial results in the timelines currently anticipated and may need to modify or delay the clinical trials or to perform additional trials. Further, Gilead may make a strategic decision to discontinue development of TAF if, for example, Gilead believes commercialization will be difficult relative to other opportunities in its pipeline. There is also risk of failing to obtain approvals from regulatory authorities for TAF, alone or in combination with other products, and the New Drug Applications for elvitegravir and cobicistat may not be approved by the U.S. Food and Drug Administration or other regulatory agencies in the timelines anticipated or at all. As a result, these product candidates as standalone agents or as part of single tablet regimens may never be successfully commercialized. These risks, uncertainties and other factors could cause actual results to differ materially from those referred to in the forward-looking statements. The reader is cautioned not to rely on these forward-looking statements. These and other risks are described in detail in Gilead's Quarterly Report on Form 10-Q for the quarter ended June 30, 2012, as filed with the U.S. Securities and Exchange Commission. All forward-looking statements are based on information currently available to Gilead, and Gilead assumes no obligation to update any such forward-looking statements.

U.S. full prescribing information for Stribild is available at www.Stribild.com.

U.S. full prescribing information for Truvada is available at www.Truvada.com.

Stribild, Truvada and Viread are trademarks or registered trademarks of Gilead Sciences, Inc.
Prezista is a registered trademark of Janssen R&D Ireland

For more information on Gilead Sciences, please visit the company's website at www.gilead.com, follow Gilead on Twitter (@GileadSciences) or call Gilead Public Affairs at 1-800-GILEAD-5 or 1-650-574-3000.

 

Contact: Gilead Sciences, Inc.
Patrick O'Brien, 650-522-1936 (Investors)
Cara Miller, 650-522-1616 (Media)

 

 

Posted: November 2012

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