Ledipasvir

Absorption

When given orally, ledipasvir reaches its maximum plasma concentration in about 4 to 4.5 hours with a maximum concentration (Cmax) of 323 ng/mL .

Toxicity

There is very little toxicity associated with the use of ledipasvir in combination products. The most common adverse reactions are headache and fatigue.

Description

Ledipasvir is a potent NS5A inhibitor that is approved for use in combination with sofosbuvir, a nucleotide inhibitor of viral polymerase, for the treatment of chronic hepatitis C virus genotype 1 infection. This combination was discovered and developed at Gilead Sciences and is marketed as the fixed combination with brand name of Harvoni.

The Uses of Ledipasvir

Ledipasvir is most commonly used in combination with sofosbuvir for treatment in chronic hepatitis C genotype 1 patients. It inhibits an important viral phosphoprotein, NS5A, which is involved in viral replication, assembly, and secretion.

Indications

When used in combination with the antiviral medication sofosbuvir, ledipasvir is indicated for the treatment of treatment of chronic hepatitis C virus (HCV) in adults and pediatric patients 3 years of age and older with the following conditions:
Its use has also proven successful in the treatment of HCV in patients co-infected with HIV .

Background

Ledipasvir is a direct acting antiviral (DAA) medication used as part of combination therapy to treat chronic Hepatitis C, an infectious liver disease caused by infection with Hepatitis C Virus (HCV). HCV is a single-stranded RNA virus that is categorized into nine distinct genotypes, with genotype 1 being the most common in the United States, and affecting 72% of all chronic HCV patients . Treatment options for chronic Hepatitis C have advanced significantly since 2011, with the development of Direct Acting Antivirals (DAAs) such as ledipasvir. More specifically, ledipasvir is an inhibitor of the Hepatitis C Virus (HCV) Non-Structural Protein 5A (NS5A), which is required for viral RNA replication and assembly of HCV virions. Although its exact mechanism of action is unknown, it is postulated to prevent hyperphosphorylation of NS5A which is required for viral protein production. It is effective against genotypes 1a, 1b, 4a, and 5a and with a lesser activity against genotypes 2a and 3a of HCV. Ledipasvir and other direct acting antivirals are very potent options for the treatment of Hepatitis C, as they exhibit a high barrier to the development of resistance . This is an important advantage relative to HCV drugs that target other viral enzymes such as the protease, for which rapid development of resistance has proven to be an important cause of therapeutic failure.
In a joint recommendation published in 2016, the American Association for the Study of Liver Diseases (AASLD) and the Infectious Diseases Society of America (IDSA) recommend ledipasvir as a first line therapy option in combination with sofosbuvir for the treatment of HCV genotypes 1a, 1b, 4, 5, and 6 . Treatment with ledipasvir is used with the intent to cure, or achieve a sustained virologic response (SVR), after 12 weeks of daily therapy. SVR and eradication of HCV infection is associated with significant long-term health benefits including reduced liver-related damage, improved quality of life, reduced incidence of Hepatocellular Carcinoma, and reduced all-cause mortality . Treatment with direct acting antivirals such as ledipasvir is associated with very minimal side effects, with the most common being headache and fatigue . Lack of significant side effects and short duration of therapy is a considerable advantage over older interferon- and ribavirin-based regimens, which were limited by infusion site reactions, reduced blood count, and neuropsychiatric effects .
Since 2014, ledipasvir has been available as a fixed dose combination product with sofosbuvir (tradename Harvoni) used for the treatment of chronic Hepatitis C. Approved in October 2014 by the FDA, Harvoni is indicated for the treatment of HCV genotypes 1, 4, 5, and 6 with or without ribavirin depending on the level of liver damage or cirrhosis . When combined together, ledipasvir and sofosbuvir as the combination product Harvoni has been shown to achieve a SVR between 93 and 99% after 12 weeks of treatment . Its use has also proven successful in the treatment of HCV in patients co-infected with HIV .

Definition

ChEBI: Ledipasvir is a benzimidazole derivative that is used in combination with sofosbuvir (under the trade name Harvoni) for the treatment of chronic hepatitis C genotype 1 infection. It has a role as an antiviral drug and a hepatitis C protease inhibitor. It is a carbamate ester, a L-valine derivative, a bridged compound, a carboxamide, a benzimidazole, a member of fluorenes, an organofluorine compound, a member of imidazoles, a N-acylpyrrolidine and an azaspiro compound.

Pharmacokinetics

Ledipasvir acts against HCV and is categorized as a direct-acting antiviral agent (DAA).
At a dose of 120 mg twice daily (2.67 times the maximum recommended dosage), ledipasvir does not prolong QTc interval to any clinically relevant extent .

Pharmacokinetics

Oral bioavailability of sofosbuvir is at least 80% based on urinary recovery. Ledipasvir also is well absorbed orally. Approximately 65% of sofosbuvir is bound to human plasma protein, and virtually all of ledipasvir is plasma protein bound.
The sofosbuvir Tmax is 0.5 to 2 hours, with peak plasma concentration of the active metabolite occurring 2 to 4 hours after dosing. The Tmax for ledipasvir is 4 to 4.5 hours. The terminal halflife for sofosbuvir and its active metabolite are 0.4 and 27 hours, respectively, and the terminal half-life for ledipasvir is 47 hours. Sofosbuvir primarily is eliminated in the urine, whereas ledipasvir elimination occurs primarily through the biliary tract. Eighty percent of sofosbuvir is recovered in the urine, primarily as the active metabolite, and 86% of ledipasvir is recovered in the feces.

Synthesis

The synthesis of the spirocyclopropane proline intermediate 136 is described in Scheme above. Bis-iodination of cyclopropane-1,1-diyldimethanol (131) in the presence of triphenylphosphine gave diiodide 132 in 70% yield. N-Boc-glycine ethyl ester (133) was then treated with sodium hydride followed by diiodide 132 to give the protected proline analog 134 in 61% yield. Saponification of the ester followed by a classical resolution with (1S,2R)-amino-indanol gave enantomerically pure salt 135. Liberation of the free acid with 1 M HCl followed by treatment with potassium tert-butoxide provided enantiopure potassium salt 136 in high yield.

Iodination of 2-bromofluorene (137) produced aryl iodide 138 in 95% yield, which was then treated with lithium hexamethyldisilazide and N-fluorobenzenesulfonimide (NFSI) to give the difluoro intermediate 139 in 82% yield. Formation of the Grignard reagent of 139 through reaction with isopropylmagnesium chloride followed by condensation with Weinreb amide 140 gave chloroketone 141 in 71% yield. The potassium salt of the cyclopropyl proline intermediate 136 was coupled with 141 to give keto ester 142 in high yield. Heating 142 with ammonium acetate resulted in formation of the imidazole ring in intermediate 143 in 77% yield.

Commercially available (1R,3S,4S)-N-Boc-2-azabicyclo [2.2.1]heptane-3-carboxylic acid (144) was coupled to 4-bromo- 1,2-benzenediamine (145) using EDC/HOBt to give a mixture of amides 146a/146b in 72% yield. Heating mixture 146a/146b with acetic acid affected cyclization to benzimidazole 147 in 94% yield. Palladium mediated coupling of bromide 147 to bis(pinacolato)diboron gave intermediate 148 which was then coupled in the same reaction vessel to bromide 143. This was followed by formation of the oxalate salt to give the protected central core of ledipasvir (149) in good overall yield. Removal of the amine protecting groups gave diamine 150 which was coupled to two equivalents of Moc-valine (151) via EDC/HOBt to give ledipasvir XVII in 73% yield.

Metabolism

In vitro, no detectable metabolism of ledipasvir was observed by human CYP1A2, CYP2C8, CYP2C9, CYP2C19, CYP2D6, and CYP3A4. Evidence of slow oxidative metabolism via an unknown mechanism has been observed. Following a single dose of 90 mg [14C]-ledipasvir, systemic exposure was almost exclusively to the parent drug (>98%). Unchanged ledipasvir is the major species present in feces .

Clinical claims and research

Ledipasvir is an HCV NS5A inhibitor, while sofosbuvir inhibits HCV NS5B polymerase. These two agents are combined in a fixed-dose combination tablet marked under the trade name Harvoni? for the treatment of patients with chronic HCV. A phase I study in healthy subjects demonstrated that a moderate-fat (600 kcal, 25–30% fat) or high-fat, high-calorie (1000 kcal, 50% fat) meal did not significantly alter the Cmax, AUC0-∞, or tmax of ledipasvir–sofosbuvir. A post hoc analysis of the phase III clinical trial data was performed to evaluate the effect of food on the pharmacokinetics and clinical outcomes of ledipasvir–sofosbuvir and revealed no significant effects.
Ledipasvir demonstrates pH-dependent solubility in vitro and therefore was evaluated in two phase I studies examining the effects of coadministration with a histamine H2-receptor antagonist (famotidine 40 mg) and a proton-pump inhibitor (omeprazole 20 mg). Administration of a single dose of the combination product ledipasvir–sofosbuvir with famotidine or omeprazole and food did not significantly alter the AUC or Cmax of either agent. Ledipasvir–sofosbuvir may be administered without regard to meals or timing of acid-reducing agents.

Mode of action

Ledipasvir is a potent inhibitor of HCV nonstructural protein 5A (NS5A), a viral phosphoprotein that plays an important but poorly understood role in viral replication, assembly, and secretion. ;Ledipasvir is approved for the treatment of genotype 1 HCV. Its safety and efficacy have not been fully established for genotypes 2 through 6. NS5A amino acid substitutions Y93H (in genotypes 1a and 1b) and Q30E (in genotype 1a) significantly reduce susceptibility to ledipasvir in cell culture and in clinical studies. Other amino acid substitutions observed in virologic treatment failures are K24R, M28T/V, Q30H/K/L (genotype 1a), and L31V/M/I (genotype 1b). Viruses with these resistance-associated mutations remained susceptible to sofosbuvir.

References

[1] hernandez d et al. , natural prevalence of ns5a polymorphisms in subjects infected with hepatitis c virus genotype 3 and their effects on the antiviral activity of ns5a inhibitors. j clin virol. 2013, 57(1): 13-8.
[2] gao m et al. , chemical genetics strategy identifies an hcv ns5a inhibitor with a potent clinical effect. nature. 2010, 465: 96-100.
[3] lawitz e j et al. , a phase 1, randomized, placebo-controlled, 3-day, dose-ranging study of gs-5885, an ns5a inhibitor, in patients with genotype 1 hepatitis c. j hepatol. 2012, 57(1): 24-31.