APPROVED AND EXPERIMENTAL THERAPIES FOR TREATMENT OF HEPATITIS B AND C, AND MUTATIONS 13. ASSOCIATED WITH DRUG RESISTANCE • Luis Menéndez-Arias HEPATITIS B Table 13.1. CURRENT DRUGS FOR TREATMENT OF HEPATITIS B Drug name Drug class Manufacturer Status Pegasys (peginterferon α-2a) Interferon Genentech FDA-approved Intron A (interferon a-2b) Interferon Merck FDA-approved Hepsera (adefovir Nucleotide analogue Gilead Sciences FDA-approved dipivoxil)a Viread (tenofovir Nucleotide analogue Gilead Sciences FDA-approved b disoproxil fumarate) a Epivir-HBV, Zeffix and Nucleoside analogue Glaxo SmithKline FDA-approved Heptodin (lamivudine) a Baraclude (entecavir) Nucleoside analogue Bristol-Myers Squibb FDA-approved Tyzeka, Sebivo Nucleoside analogue Novartis FDA-approved (telbivudine) Vemlidy (TAF, tenofovir Tenofovir prodrug Gilead Sciences FDA-approved alafenamide, GS-7340) Emtriva (emtricitabine; Nucleoside analogue Gilead Sciences FDA-approved b FTC) a Levovir, Revovir Nucleoside analogue Bukwang Studies cancelled c (clevudine, L-FMAU) pharmaceuticals, Eisai (Japan) Besivo (LB80380, Nucleoside analogue IIDong Pharmaceutical Approved in S ANA380) Co. Ltd. Korea Zadaxin (thymosin alpha) Immune enhancer SciClone Approved outside U.S. ABX 203 Therapeutic vaccine ABIVAX Phase IIb/III ARC-520 RNAi gene silencer Arrowhead Research Phase II/III 641 Drug name Drug class Manufacturer Status Myrcludex B Entry inhibitor Hepatera (Russia), Phase IIa Myr-Gmbh (Germany) (Russia) NVR-1221 (NVR 3-778) Capsid inhibitor Novira Therapeutics Phase IIa AGX-1009 Tenofovir prodrug SHRG/YSY (China) Phase II, China TXL (CMX157) Tenofovir prodrug ContraVir Phase II Pharmaceuticals Pradefovir mesylate Adefovir prodrug Valeant Phase II (DB05478) Pharmaceuticals Morphothiadine mesilate Capsid inhibitor Sunshine Lake Phase II (GLS4) Pharma of HEC, China ISIS-HBV Rx RNA-based antisense ISIS Pharma with Phase II Glaxo SmithKline SB 9200 HBV Small nucleic acid Spring Bank Pharma Phase II hybrid ARB-1467 & ARB-1740 RNAi gene silencer Arbutus Biopharma Phase II Rep 2139-Ca HBsAg release REPLICor Inc Phase II inhibitor Rep 2165-Ca HBsAg release REPLICor Inc Phase II inhibitor GS-4774 Therapeutic vaccine Gilead Sciences Phase II with Globe Immune GS-9620 TLR7 agonist Gilead Sciences Phase II RO6864018 (RG7795, TLR7 agonist Roche Phase II ANA773) Nasvac Therapeutic vaccines CGEB, Cuba Phase II CYT107 (Interleukin-7) Immunomodulator Cytheris Phase I/IIa INO-1800 Therapeutic vaccine Inovio Phase I AIC 649 Capsid Inhibitor AiCuris Phase I HB-110 Therapeutic vaccine Ichor Medical Systems Phase I (with Janssen) TG 1050 Therapeutic vaccine Transgen Phase I 642 FDA, United States Food and Drug Administration. a This is an anti-HIV drug. For information on HIV drug-resistance, see Tables in Chapter 4. b This drug has been approved only for treatment of HIV infection, but is also an inhibitor of the hepatitis B virus polymerase. c Approved in South Korea and the Philippines for treatment of chronic hepatitis B. d Orphan drug approved in the U.S. for cancer treatment. Clinical studies on the efficacy of the drug in combination with nucleoside analogues are available [Wu et al. Expert Opin Biol Ther 2015; 15 (suppl 1): S129-S132]. References: Hepatitis B Foundation Drug Watch (http://www.hepb.org); Hadziyannis et al. Adv Pharmacol 2013; 67: 247-291; Liu et al. Int J Biochem Cell Biol 2013; 45: 1987- 1996; Menéndez-Arias et al. Curr Opin Virol 2014; 8: 1-9; Trépo et al. Lancet 2014; 384: 2053-2063; Block et al. Antiviral Res 2015; 121: 69-81; Isorce et al. Antiviral Res 2015; 122: 69-81; Jia et al. Future Med Chem 2015; 7: 587-607; Liang et al. Hepatology 2015; 62: 1893-1908; Wang et al. Virus Res 2016; 213: 205-213; Zoulim et al. Curr Opin Virol 2016; 18: 109-116; Testoni et al. Liver Int 2017; 37 (suppl. 1): 33-39; Scott & Chan. Drugs 2017; 77: 1017-1028. Resistance to interferon To date, ten hepatitis B virus (HBV) genotypes (A-J) have been identified. HBV genotypes are classified by more than 8% divergence of the full nucleotide sequence. Their geographic distribution varies significantly. HBV genotype A is common in Northern Europe, North America and Central Africa, whereas genotype D is found mainly in the Mediterranean area, Middle East and India. Genotypes B and C are prevalent in Asia, genotype E in West Africa, and genotype F in Central and South America and Polynesia. Genotype G was identified in Europe and North America. Genotype H has been recently identified in Central America. HBV genotypes can be further classified into sub-genotypes if a divergence of 4% is observed. Major sub-genotypes are A1 to A7 (genotype A), B1 to B9 (genotype B), C1 to C16 (genotype C), D1 to D8 (genotype D), and F1 to F4 (genotype F). Available evidence indicates a better sustained response to conventional interferon in patients with genotype B than those with C, and in patients with genotype A than those with D. In contrast, there are conflicting data regarding the response to pegylated interferon. The molecular basis of the observed differences are not known, although the lower response of genotype C patients has been related to the higher frequency of the basal core promoter mutations (A1762T/G1764A). Genotypes C and D also carry a higher risk of cirrhosis and development of hepatocellular carcinoma than genotypes A and B. A specialized database (HBVdb; http://hbvdb.ibcp.fr) dealing with the genetic variability of hepatitis B virus and its resistance to treatment has been established (Hayer et al. Nucleic Acids Res 2013; 41: D566-D570). The database allows sequence analysis and queries about drug resistance profiles. 643 A recent study has described an association between hepatitis B virus spliced variants and impaired response to interferon therapy (Chen et al. Sci Rep 2015; 5: 16459). References: Coffin & Lee. Liver Int 2009; 29: 116-124; Shamliyan et al. Ann Intern Med 2009; 150: 111-124; Cooksley. J Viral Hepat 2010; 17: 601-610; Lin & Kao. J Gastroenterol Hepatol 2011; 26 (suppl. 1): 123-130; Liu et al. Curr Opin Immunol 2011; 23: 57-64; Wong & Sung. Curr Opin Infect Dis 2012; 25: 570-577; You et al. World J Gastroenterol 2014; 20: 13293-13305; Lin & Kao. Cold Spring Harb Perspect Med 2015; 5: a021436; Zhang et al. World J Gastroenterol 2016; 22: 126-144; Tian & Jia. Hepatol Int 2016; 10: 854-860. Resistance to nucleoside analogue inhibitors As in the case of HIV-1 and HIV-2, resistance to nucleoside analogue inhibitors maps within the viral polymerase. Hepatitis B virus (HBV) polymerase and HIV-1 reverse transcriptase share homology regions designated as motifs A, B, C, D and E (Fig. 16.1). Motif C contains the YMDD sequence which mutates in response to treatment with lamivudine and other HBV polymerase inhibitors. Figure 13.1. Alignments of conserved motifs within hepatitis B virus (HBV) polymerase and HIV-1 reverse transcriptase. Conserved residues are boxed. Sequences were taken from EMBL/GenBank accession files J02205 (HBV subtype adw2) and M15654 (isolate BH10), and the alignments were based on those given by Poch et al. EMBO J 1989; 8: 3867-3874. Numbering of motifs in the HBV polymerase is given according to the standardized nomenclature of Stuyver et al. Hepatology 2001; 33: 751-757. From a clinical point of view, the most relevant mutation is rtM204V which appears during treatment with lamivudine, and maps in the YMDD region. In many patients, it is accompanied by a second mutation (rtL180M), particularly in those previously treated with famciclovir. The emergence of these mutations is clinically associated with elevated 644 levels of alanine aminotransferase and viral DNA titers in serum. The YMDD mutation has a high prevalence of 56% among patients treated with lamivudine for 256 weeks and 70% in patients treated for more than 4 years (Leung et al. Hepatology 2001; 33: 1527- 1532). Studies focusing on the dynamics of HBV quasispecies variant populations have revealed that virological breakthrough was preceded by 2-4 months by the emergence of quasispecies variants bearing amino acid substitutions at RT position 204, i.e. within the YMDD catalytic motif (rtM204V/I) (Pallier et al. J Virol 2006; 80: 643-653). Compared with hepatitis B genotype C, genotype B appears to develop an earlier biochemical resistance to lamivudine (Hsieh et al. Antivir Ther 2009; 14: 1157-1163). Table 13.2. HEPATITIS B VIRUS (HBV) POLYMERASE MUTATIONS ASSOCIATED WITH RESISTANCE TO NUCLEOSIDE INHIBITORS Mutations a Comments rtS78T In a study involving >350 chronically HBV-infected patients in Europe, this (S426T) mutation showed more than ten-fold increased prevalence in adefovir-failing patients (Cento et al. J Infect 2013; 67: 303-312). The prevalence of this mutation was lower in lamivudine-treated patients (2.7%) in comparison with naïve individuals (7.9%). It can generate a truncated surface protein due to a stop codon at position 69 (sC69*) (Ding et al. Antiviral Res 2014; 102: 29-34). rtL80V/I Amino acid substitution associated with lamivudine resistance and enhanced (L428V/I) viral replication in vitro. Usually, rtL80V/I occur in virus containing the rtM204V mutation (Warner et al. Antimicrob Agents Chemother 2007; 51: 2285-2292). Associated in patients with poor response to adefovir (Lee et al. Liver Int 2009; 29: 552-556; Mirandola et al. Antiviral Res 2012; 96: 422- 429) and found as a minority variant in patients treated with telbivudine (Yin et al. J Gen Virol 2015; 96: 3302-3312). The rtL80I and rtL80V substitutions confer moderate resistance to telbivudine (Yin et al. J Gen Virol 2015; 96: 3302-3312). rtS117F Compensatory mutation for rtM204I appearing during lamivudine therapy (S465F) (Lin et al. J Antimicrob Chemother 2012; 67: 39-48). rtH124N Polymorphism associated with a reduced response to entecavir, in a study H472N carried out in Hong Kong (Wong et al. J Infect Dis 2014; 210: 701-707).