Newswise — GlaxoSmithKline (GSK) today announced that the Food and Drug Administration has granted marketing clearance for Lexivaâ„¢ (fosamprenavir calcium) (Lex-ee'-va, formerly GW433908, or 908), a new protease inhibitor (PI) for the treatment of HIV infection in adults in combination with other antiretroviral medications. The following points should be considered when initiating therapy with Lexiva/ritonavir (Lexiva/r) in PI-experienced patients: the PI-experienced patient study was not large enough to reach a definitive conclusion that Lexiva/r and lopinavir/ritonavir are clinically equivalent. Once-daily administration of Lexiva plus ritonavir is not recommended for PI-experienced patients. Lexiva was co-discovered by GSK and Vertex Pharmaceuticals (Nasdaq: VRTX).
Lexiva, a PI that can be taken once or twice daily without food or water restrictions, has been evaluated in clinical trials with both PI-experienced and antiretroviral therapy (ART)-naïve HIV patients.
Lexiva may be dosed three different ways: 1) two 700mg tablets twice daily (BID), 2) two 700mg tablets once daily (QD) in combination with two 100mg capsules of ritonavir QD (Lexiva/r QD), or 3) one 700mg tablet BID in combination with one 100mg capsule of ritonavir BID (Lexiva/r BID). For PI-experienced patients, the recommended dose is one 700mg tablet BID in combination with one 100mg capsule of ritonavir BID.
"The drug's QD and BID dosing options with no food or water restrictions, and a low pill burden demonstrate GSK's ongoing commitment to providing flexible anti-HIV therapies for patients," said Doug Manion, M.D., vice president of clinical development and medical affairs at GSK.
More than 1,200 people " both ART-naïve and PI-experienced patients " participated in three Phase III trials to test the safety and efficacy of Lexiva with and without ritonavir. In all three trials, study drugs were taken as part of combination therapy that included two nucleoside reverse transcriptase inhibitors. In these clinical trials Lexiva demonstrated: * Durable anti-viral response through 48 weeks of therapy in ART-naive patients (<400 copies/mL 66 percent to 69 percent)* All grade 2-4 drug-related adverse events < 10 percent in ART-naïve patients- Significantly less grade 2-4 drug-related diarrhea than nelfinavir* All grade 2-4 drug-related adverse events < 13 percent in PI-experienced patients* Flexible once or twice daily options in ART-naïve patients with no food or fluid restrictions* No ART-naive patients receiving Lexiva/r developed any PI mutations. In PI-experienced patients, the following amprenavir resistance associated mutations were selected either alone or in combination: V32I, M46I/L, I47V, I50V, I54L/M and I84V. The clinical significance of resistance data is currently under evaluation.
"It's important for patients to comply with therapy because current treatment is lifelong," said Jeffrey P. Nadler, M.D., professor of medicine and director of clinical research in infectious diseases, University of South Florida College of Medicine, Tampa. "Patients need something they can tolerate, so that they are able to take the medicines as prescribed. Lexiva fits that picture," he said.
The following results were reported for each of the Phase III trials at 48-weeks:
The NEAT Study NEAT compared Lexiva with nelfinavir (NFV) in 249 ethnically and gender diverse, ART-naïve patients, with advanced HIV disease (45 percent of patients had viral load >100,000 copies/mL, 48 percent had CD4+ cell count <200 cells/mm3, and 20 percent were CDC Class C) at entry. Patients took 1,400mg of Lexiva BID or 1,250mg of NFV BID in combination with abacavir sulfate and lamivudine BID. * 66 percent of patients taking Lexiva achieved undetectable viral load (<400 copies/mL), compared to 52 percent of patients taking NFV.* Among patients with high baseline viral load (>100,000 copies/mL), 67 percent of 73 patients in the arm containing Lexiva achieved undetectable viral load (<400 copies/mL), compared to 36 percent of 37 patients in the NFV arm.* There was significantly less grade 2-4 drug-related diarrhea in patients receiving Lexiva (5 percent) than in patients receiving NFV (18 percent). * Protease mutations selected at the first failure timepoint with Lexiva (V32I+147V or 154L/M) had limited cross-resistance to other PIs.* The most common adverse events were diarrhea, nausea, vomiting, headache and rash.
The SOLO Study The SOLO Study reported results of 649 ethnically and gender diverse ART-naïve patients, with advanced HIV disease (43 percent of patients had viral load >100,000 copies/mL, 55 percent had CD4+ cell count <200 cells/mm3, and 22 percent were CDC Class C) at entry. Patients in the study took either 1,400mg Lexiva with 200mg ritonavir (Lexiva/r) QD, or 1,250mg NFV BID. Both PIs were administered in combination with abacavir sulfate and lamivudine BID.* 69 percent of patients taking Lexiva/r achieved undetectable viral load (<400 copies/mL), compared to 68 percent of patients taking NFV.* Among patients with a high viral load (>100,000 copies/mL) at baseline, 66 percent of 125 patients taking Lexiva/r QD achieved undetectable viral load (<400 copies/mL), compared to 64 percent of 133 patients taking NFV BID. * There was significantly less grade 2-4 drug-related diarrhea in patients receiving Lexiva (10 percent) than in patients receiving NFV (18 percent).* No protease mutations were observed through 48 weeks in the 32 patients who experienced virologic failure with Lexiva/r QD.* There were significantly fewer nucleoside reverse transcriptase inhibitor (NRTI) mutations observed after virologic failure with Lexiva/r QD (4 of 32 patients, or 13 percent) compared with NFV (30 of 54, or 56 percent).* The most common adverse events were diarrhea, nausea, vomiting, headache and rash.
The CONTEXT Study CONTEXT enrolled 315 PI-experienced patients with prior virologic failure. The study compared Lexiva with ritonavir to the PI lopinavir/ritonavir (LPV/r). The PIs were given in combination with two NRTIs. The following points should be considered when initiating therapy with Lexiva/r in PI-experienced patients: the PI-experienced patient study was not large enough to reach a definitive conclusion that Lexiva/r and lopinavir/ritonavir are clinically equivalent. Once-daily administration of Lexiva plus ritonavir is not recommended for PI-experienced patients.* 58 percent of patients receiving Lexiva/r BID achieved undetectable viral load (<400 copies/mL) compared to 61 percent of patients taking LPV/r BID. * 46 percent of patients taking Lexiva/r BID achieved viral loads below 50 copies/mL compared to 50 percent taking LPV/r BID.* The overall incidence of drug-related adverse events of at least moderate severity was comparable between patients receiving Lexiva/r BID and LPV/r BID.* The most common adverse events were diarrhea, nausea, vomiting, headache and rash.
Lexiva is contraindicated in patients with previously demonstrated clinically significant hypersensitivity to any of the components of this product or to amprenavir. New onset or exacerbations of diabetes mellitus and hyperglycemia, and spontaneous bleeding in hemophiliacs have been reported with protease inhibitors. Redistribution/accumulation of body fat including central obesity, dorsocervical fat enlargement (buffalo hump), peripheral wasting, facial wasting, breast enlargement, and "cushingoid appearance" have been observed in patients receiving antiretroviral therapy. The causal relationship, mechanism, and long-term consequences of these events are currently unknown. Lexiva is contraindicated with ergot derivatives, cisapride, pimozide, midazolam, and triazolam. If Lexiva is coadministered with ritonavir, flecainide and propafenone are also contraindicated.
GSK will market Lexiva and GSK and Vertex will co-promote it in the United States and key markets in Europe.
GlaxoSmithKline is one of the world's leading research-based pharmaceutical and healthcare companies and an industry leader in HIV research and therapies. The company is engaged in basic research programs designed to investigate new targets to treat HIV.
For full prescribing information, please call Mary Faye Dark, GSK (919-483-2839) or Beth Schlesinger, PCI (312-558-1770).
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