Design of Peptide-based Inhibitors for Human Immunodeficiency Virus Type 1 Strains Resistant to T-20

Abstract

Enfuvirtide (T-20) is a fusion inhibitor that suppresses replication of human immunodeficiency virus (HIV) variants with multi-drug resistance to reverse transcriptase and protease inhibitors. It is a peptide derived from the C-terminal heptad repeat (C-HR) of HIV-1 gp41, and it prevents interactions between the C-HR and the N-terminal HR (N-HR) of gp41, thus interfering with conformational changes that are required for viral fusion. However, prolonged therapies with T-20 result in the emergence of T-20-resistant strains that contain primary mutations such as N43D in the N-HR of gp41 (where T-20 and C-HR bind) that help the virus escape at a fitness cost. Such variants often go on to acquire a secondary mutation, S138A, in the C-HR of gp41 region that corresponds to the sequence of T-20. We demonstrate here that the role of S138A is to compensate for the impaired fusion kinetics of HIV-1s carrying primary mutations that abrogate binding of T-20. To preempt this escape strategy, we designed a modified T-20 variant containing the S138A substitution and showed that it is a potent inhibitor of both T-20-sensitive and T-20-resistant viruses. Circular dichroism analysis revealed that the S138A provided increased stability of the 6-helix bundle. We validated our approach on another fusion inhibitor, C34. In this case, we designed a variant of C34 with the secondary escape mutation N126K and showed that it can effectively inhibit replication of C34-resistant HIV-1. These results prove that it is possible to design improved peptide-based fusion inhibitors that are efficient against a major mechanism of drug resistance. Enfuvirtide (T-20) is a fusion inhibitor that suppresses replication of human immunodeficiency virus (HIV) variants with multi-drug resistance to reverse transcriptase and protease inhibitors. It is a peptide derived from the C-terminal heptad repeat (C-HR) of HIV-1 gp41, and it prevents interactions between the C-HR and the N-terminal HR (N-HR) of gp41, thus interfering with conformational changes that are required for viral fusion. However, prolonged therapies with T-20 result in the emergence of T-20-resistant strains that contain primary mutations such as N43D in the N-HR of gp41 (where T-20 and C-HR bind) that help the virus escape at a fitness cost. Such variants often go on to acquire a secondary mutation, S138A, in the C-HR of gp41 region that corresponds to the sequence of T-20. We demonstrate here that the role of S138A is to compensate for the impaired fusion kinetics of HIV-1s carrying primary mutations that abrogate binding of T-20. To preempt this escape strategy, we designed a modified T-20 variant containing the S138A substitution and showed that it is a potent inhibitor of both T-20-sensitive and T-20-resistant viruses. Circular dichroism analysis revealed that the S138A provided increased stability of the 6-helix bundle. We validated our approach on another fusion inhibitor, C34. In this case, we designed a variant of C34 with the secondary escape mutation N126K and showed that it can effectively inhibit replication of C34-resistant HIV-1. These results prove that it is possible to design improved peptide-based fusion inhibitors that are efficient against a major mechanism of drug resistance. HIV-1 2The abbreviations used are: HIV, human immunodeficiency virus; T-20, enfuvirtide; HR, heptad repeat; MAGI, multinuclear activation of galactosidase indicator; EC50, 50% effective concentration; Tm, melting temperature; CD, circular dichroism; shRNA, short hairpin RNA; WT, wild-type.2The abbreviations used are: HIV, human immunodeficiency virus; T-20, enfuvirtide; HR, heptad repeat; MAGI, multinuclear activation of galactosidase indicator; EC50, 50% effective concentration; Tm, melting temperature; CD, circular dichroism; shRNA, short hairpin RNA; WT, wild-type. entry into the target cells is mediated by two envelope glycoproteins, gp120 and gp41, that form a trimeric gp120·gp41 complex. After binding of gp120 to the CD4 receptor and CCR5 (or CXCR4) coreceptor on the surface of the target cell, the gp41 trimer forms an extended conformation of the three helices that allows a hydrophobic fusion peptide to be inserted into the target cell membrane, generating an intermediate that is anchored to both cellular and viral membranes. After this step, the gp41 is believed to start refolding to a more stable 6-helix bundle composed of the α-helical trimer of the N-terminal heptad repeat (N-HR) folded into an anti-parallel conformation with the three C-terminal heptad repeats (C-HR) (1Chan D.C. Kim P.S. Cell. 1998; 93: 681-684Abstract Full Text Full Text PDF PubMed Scopus (1110) Google Scholar, 2Weiss C.D. AIDS Rev. 2003; 5: 214-221PubMed Google Scholar). This refolding brings the viral and cellular membranes together to catalyze fusion. The transition of the extended intermediate to the 6-helix bundle can be inhibited by the addition of exogenous peptides derived from gp41 C-HR (Fig. 1A) that prevent the formation of the 6-helix bundle and inhibit the HIV-1 fusion with the target cells (3Jiang S. Lin K. Strick N. Neurath A.R. Nature. 1993; 365: 113Crossref PubMed Scopus (475) Google Scholar, 4Chan D.C. Chutkowski C.T. Kim P.S. Proc. Natl. Acad. Sci. U. S. A. 1998; 95: 15613-15617Crossref PubMed Scopus (484) Google Scholar, 5Dwyer J.J. Wilson K.L. Davison D.K. Freel S.A. Seedorff J.E. Wring S.A. Tvermoes N.A. Matthews T.J. Greenberg M.L. Delmedico M.K. Proc. Natl. Acad. Sci. U. S. A. 2007; 104: 12772-12777Crossref PubMed Scopus (219) Google Scholar, 6Otaka A. Nakamura M. Nameki D. Kodama E. Uchiyama S. Nakamura S. Nakano H. Tamamura H. Kobayashi Y. Matsuoka M. Fujii N. Angew. Chem. Int. Ed. Engl. 2002; 41: 2937-2940Crossref PubMed Google Scholar). T-20, a 36-amino acid peptide derived from C-HR, effectively suppresses in vivo replication of HIV-1 resistant to inhibitors of reverse transcriptase and protease (7Lalezari J.P. Henry K. O'Hearn M. Montaner J.S. Piliero P.J. Trottier B. Walmsley S. Cohen C. Kuritzkes D.R. Eron Jr., J.J. Chung J. DeMasi R. Donatacci L. Drobnes C. Delehanty J. Salgo M. N. Engl. J. Med. 2003; 348: 2175-2185Crossref PubMed Scopus (825) Google Scholar, 8Lazzarin A. Clotet B. Cooper D. Reynes J. Arasteh K. Nelson M. Katlama C. Stellbrink H.J. Delfraissy J.F. Lange J. Huson L. DeMasi R. Wat C. Delehanty J. Drobnes C. Salgo M. N. Engl. J. Med. 2003; 348: 2186-2195Crossref PubMed Scopus (608) Google Scholar). However, HIV-1 variants resistant to T-20 have recently emerged carrying primary mutations in the Leu-33–Leu-45 region of the N-HR domain (9Baldwin C.E. Berkhout B. Retrovirology. 2006; 3: 84Crossref PubMed Scopus (17) Google Scholar, 10Cabrera C. Marfil S. Garcia E. Martinez-Picado J. Bonjoch A. Bofill M. Moreno S. Ribera E. Domingo P. Clotet B. Ruiz L. AIDS. 2006; 20: 2075-2080Crossref PubMed Scopus (40) Google Scholar, 11Labrosse B. Morand-Joubert L. Goubard A. Rochas S. Labernardiere J.L. Pacanowski J. Meynard J.L. Hance A.J. Clavel F. Mammano F. J. Virol. 2006; 80: 8807-8819Crossref PubMed Scopus (48) Google Scholar, 12Mink M. Mosier S.M. Janumpalli S. Davison D. Jin L. Melby T. Sista P. Erickson J. Lambert D. Stanfield-Oakley S.A. Salgo M. Cammack N. Matthews T. Greenberg M.L. J. Virol. 2005; 79: 12447-12454Crossref PubMed Scopus (111) Google Scholar, 13Nameki D. Kodama E. Ikeuchi M. Mabuchi N. Otaka A. Tamamura H. Ohno M. Fujii N. Matsuoka M. J. Virol. 2005; 79: 764-770Crossref PubMed Scopus (77) Google Scholar, 14Perez-Alvarez L. Carmona R. Ocampo A. Asorey A. Miralles C. Perez de Castro S. Pinilla M. Contreras G. Taboada J.A. Najera R. J. Med. Virol. 2006; 78: 141-147Crossref PubMed Scopus (41) Google Scholar, 15Xu L. Pozniak A. Wildfire A. Stanfield-Oakley S.A. Mosier S.M. Ratcliffe D. Workman J. Joall A. Myers R. Smit E. Cane P.A. Greenberg M.L. Pillay D. Antimicrob. Agents Chemother. 2005; 49: 1113-1119Crossref PubMed Scopus (155) Google Scholar). Among them, V38A and N43D seem to be major primary mutations for T-20 resistance. Meanwhile, a secondary mutation at the C-HR region (S138A) has been reported to enhance T-20 resistance with an as yet undefined mechanism (9Baldwin C.E. Berkhout B. Retrovirology. 2006; 3: 84Crossref PubMed Scopus (17) Google Scholar, 14Perez-Alvarez L. Carmona R. Ocampo A. Asorey A. Miralles C. Perez de Castro S. Pinilla M. Contreras G. Taboada J.A. Najera R. J. Med. Virol. 2006; 78: 141-147Crossref PubMed Scopus (41) Google Scholar, 15Xu L. Pozniak A. Wildfire A. Stanfield-Oakley S.A. Mosier S.M. Ratcliffe D. Workman J. Joall A. Myers R. Smit E. Cane P.A. Greenberg M.L. Pillay D. Antimicrob. Agents Chemother. 2005; 49: 1113-1119Crossref PubMed Scopus (155) Google Scholar) (Fig. 1B). The mechanism of resistance to C34, another C-HR peptide-based inhibitor of HIV fusion, has been the subject of multiple studies (13Nameki D. Kodama E. Ikeuchi M. Mabuchi N. Otaka A. Tamamura H. Ohno M. Fujii N. Matsuoka M. J. Virol. 2005; 79: 764-770Crossref PubMed Scopus (77) Google Scholar, 16Armand-Ugon M. Gutierrez A. Clotet B. Este J.A. Antiviral Res. 2003; 59: 137-142Crossref PubMed Scopus (66) Google Scholar). Because of a 22-amino acid overlap between the T-20 and C34 peptides (Fig. 1B), HIV-1 has developed primary mutations for C34 resistance in vitro at the identical Leu-33–Leu-45 region of the peptides. During in vitro selection of C34 resistance, we identified a mutation in the C-HR domain, N126K, that is also observed in some T-20-resistant clinical variants (10Cabrera C. Marfil S. Garcia E. Martinez-Picado J. Bonjoch A. Bofill M. Moreno S. Ribera E. Domingo P. Clotet B. Ruiz L. AIDS. 2006; 20: 2075-2080Crossref PubMed Scopus (40) Google Scholar, 15Xu L. Pozniak A. Wildfire A. Stanfield-Oakley S.A. Mosier S.M. Ratcliffe D. Workman J. Joall A. Myers R. Smit E. Cane P.A. Greenberg M.L. Pillay D. Antimicrob. Agents Chemother. 2005; 49: 1113-1119Crossref PubMed Scopus (155) Google Scholar, 17Baldwin C.E. Sanders R.W. Deng Y. Jurriaans S. Lange J.M. Lu M. Berkhout B. J. Virol. 2004; 78: 12428-12437Crossref PubMed Scopus (129) Google Scholar). We showed that N126K conferred resistance to C34 by compensating for the impaired intra-gp41 interaction by a primary mutation, I37K (13Nameki D. Kodama E. Ikeuchi M. Mabuchi N. Otaka A. Tamamura H. Ohno M. Fujii N. Matsuoka M. J. Virol. 2005; 79: 764-770Crossref PubMed Scopus (77) Google Scholar). N126K was initially identified in background of V38A, another primary mutation, for T-20 resistance in vivo (17Baldwin C.E. Sanders R.W. Deng Y. Jurriaans S. Lange J.M. Lu M. Berkhout B. J. Virol. 2004; 78: 12428-12437Crossref PubMed Scopus (129) Google Scholar). Baldwin et al. (17Baldwin C.E. Sanders R.W. Deng Y. Jurriaans S. Lange J.M. Lu M. Berkhout B. J. Virol. 2004; 78: 12428-12437Crossref PubMed Scopus (129) Google Scholar, 18Baldwin C. Berkhout B. J. Virol. 2008; 82: 7735-7740Crossref PubMed Scopus (23) Google Scholar) demonstrated a striking T-20-dependent replication phenotype in the V38A/N126K variant and proposed that T-20 acts as a safety pin to prevent premature formation of helical bundle, as N126K enhanced binding capacity of the introduced C-HR to N36 with V38A. Taken together, these studies suggest that mutations in the C-HR serve as secondary mutations. In this study we show that the main role of secondary mutations that follow the appearance of primary mutations during treatment with peptide-based fusion inhibitors is to compensate for the impairment in replication kinetics that is caused by the primary mutations (supplemental Fig. 1). Based on this finding we hypothesized that analogs of T-20 carrying substitutions corresponding to secondary T-20 resistance mutations should be active against both wild-type and T-20-resistant viruses containing primary mutations. Indeed, our results confirmed our hypothesis and showed that T-20 with the S138A substitution (T-20S138A) has a strong anti-HIV-1 activity even against T-20-resistant clones. Moreover, we demonstrate that this restoration is concomitant to improved binding of C-HRS138A to N-HRN43D, suggesting that our approach utilizing the resistance-associated mutations to design peptides into effective peptide-based and cells in cells in modified cells provided by M. the AIDS and of of and used for the drug as (13Nameki D. Kodama E. Ikeuchi M. Mabuchi N. Otaka A. Tamamura H. Ohno M. Fujii N. Matsuoka M. J. Virol. 2005; 79: 764-770Crossref PubMed Scopus (77) Google Scholar, J. M. J. Virol. PubMed Google Scholar, Y. H. J. 1998; PubMed Scopus Google Scholar). HIV-1 A. S. T. R. A. J. Virol. 59: PubMed Google was used for of HIV-1 Antiviral peptides used in this study as A. Nakamura M. Nameki D. Kodama E. Uchiyama S. Nakamura S. Nakano H. Tamamura H. Kobayashi Y. Matsuoka M. Fujii N. Angew. Chem. Int. Ed. Engl. 2002; 41: 2937-2940Crossref PubMed Google Scholar). of of peptide of was by the multinuclear activation of galactosidase as (13Nameki D. Kodama E. Ikeuchi M. Mabuchi N. Otaka A. Tamamura H. Ohno M. Fujii N. Matsuoka M. J. Virol. 2005; 79: 764-770Crossref PubMed Scopus (77) Google Scholar). the target cells in the the cells with the HIV-1 cells of and in the of of in viral the cells with in The activity of was as the that HIV-1 replication by 50% effective of HIV-1 HIV-1 carrying as (13Nameki D. Kodama E. Ikeuchi M. Mabuchi N. Otaka A. Tamamura H. Ohno M. Fujii N. Matsuoka M. J. Virol. 2005; 79: 764-770Crossref PubMed Scopus (77) Google Scholar). was into cells with After the and at Circular peptide was with and the a with a The stability was by the in the circular dichroism at The of the transition of was as A. Nakamura M. Nameki D. Kodama E. Uchiyama S. Nakamura S. Nakano H. Tamamura H. Kobayashi Y. Matsuoka M. Fujii N. Angew. Chem. Int. Ed. Engl. 2002; 41: 2937-2940Crossref PubMed Google Scholar). cells with virus for The cells and in a of The on and the of A. Kodama Y. Matsuoka M. M. H. S. J. Virol. 2008; 82: PubMed Scopus Google Scholar). HIV-1 replication two of that been and to cells as (13Nameki D. Kodama E. Ikeuchi M. Mabuchi N. Otaka A. Tamamura H. Ohno M. Fujii N. Matsuoka M. J. Virol. 2005; 79: 764-770Crossref PubMed Scopus (77) Google Scholar, A. Kodama Y. Matsuoka M. M. H. S. J. Virol. 2008; 82: PubMed Scopus Google Scholar) with To that the two of a of was with three and of the of the cells and with and the cellular was The was to and The HIV-1 a on was the was to cells The cells at the of to and the viral was of gp41 S138A gp41 was the of of the D.C. D. J.M. Kim P.S. Cell. Full Text Full Text PDF PubMed Scopus Google Scholar) The of the the in and by the with the T. H. R. Jr., A. C. B. J. Chem. 2005; PubMed Scopus Google Scholar) the in the gp41 was with of with and the of the as The S138A was by the the with the on of the three of and and the The was of at on Antiviral peptide analogs of T-20 with acid substitutions at the and for to inhibit three major T-20-resistant the (13Nameki D. Kodama E. Ikeuchi M. Mabuchi N. Otaka A. Tamamura H. Ohno M. Fujii N. Matsuoka M. J. Virol. 2005; 79: 764-770Crossref PubMed Scopus (77) Google Scholar) 1). The results that inhibited replication of T-20-resistant as as the wild-type to enhanced T-20 activity against T-20-resistant by as with the T-20. to hydrophobic and anti-HIV-1 to anti-HIV-1 activity to T-20-resistant clones. The substitution the anti-HIV-1 activity of the peptide activity of peptides against T-20-resistant gp41 the replication mutation, observed in the of HIV-1 was introduced into the background used in this study (77) To the replication mutation, observed in the of HIV-1 was introduced into the background used in this study in a acid at of T-20 showed and substitutions the anti-HIV-1 activity of T-20 against and T-20-resistant clones. acid and the anti-HIV-1 activity even against These results suggest that hydrophobic more are in this the α-helical is for the as a mutation to is to the A. P. G. C. G. J. 1998; PubMed Scopus Google Scholar) in an T-20 Circular the mechanism by the substitutions at the activity of T-20 we the binding of these peptides to N-HR circular dichroism analysis (Fig. the of stable α-helical of the 6-helix bundle that is a for activity and is to be and with HIV-1 fusion Kim P.S. Rev. PubMed Scopus Google Scholar). at interaction of N-HR and C-HR Because T-20 in vitro with the N36 is derived from of we used a of C34, a peptide that with T-20 and also HIV fusion by the The C34 the T-20 substitutions (Fig. 1B). with a of N36 and showed binding with at was observed in and and (Fig. To the stability of the helical from the N36 and C34 we the melting of (supplemental 1). The transition of the at with the stability of the helical from the N36 and C34 in are of the binding of these peptides. The melting the 50% of 6-helix bundle was of N36 and C34 containing the S138A substitutions showed with that of the wild-type complex. the addition of the S138A also improved the stability of the complex. These results a striking between the stability and the anti-HIV-1 activity of the Fig. The of the from and C34 that virus containing the N43D mutation resistance to T-20, to that are to the formation of the 6-helix containing T-20 Antiviral of C34 at that binding of C34 to N-HR is of T-20 binding to we the anti-HIV-1 of peptides that have S138A The and peptides showed potent anti-HIV-1 to and (supplemental Based on these we that the stability of of modified and containing T-20 resistance mutations a of the binding of to Antiviral of C34 with have recently identified another mutation at the N-HR of gp41 during of HIV-1 to C34 in vitro (13Nameki D. Kodama E. Ikeuchi M. Mabuchi N. Otaka A. Tamamura H. Ohno M. Fujii N. Matsuoka M. J. Virol. 2005; 79: 764-770Crossref PubMed Scopus (77) Google Scholar). The N126K has been observed prolonged (10Cabrera C. Marfil S. Garcia E. Martinez-Picado J. Bonjoch A. Bofill M. Moreno S. Ribera E. Domingo P. Clotet B. Ruiz L. AIDS. 2006; 20: 2075-2080Crossref PubMed Scopus (40) Google Scholar, 15Xu L. Pozniak A. Wildfire A. Stanfield-Oakley S.A. Mosier S.M. Ratcliffe D. Workman J. Joall A. Myers R. Smit E. Cane P.A. Greenberg M.L. Pillay D. Antimicrob. Agents Chemother. 2005; 49: 1113-1119Crossref PubMed Scopus (155) Google Scholar). we have confirmed that the peptide can also a C34-resistant containing peptides designed to have mutations seem to have potent However, is the acid sequence of T-20 (Fig. 1B), we the of N126K substitution on T-20 activity of peptides against C34-resistant gp41 the replication the mutation, observed in of HIV-1 was introduced into the background used in this study HIV-1 was with the virus as in the region of To the replication the mutation, observed in of HIV-1 was introduced into the background used in this study C34-resistant HIV-1 was with the virus as (13Nameki D. Kodama E. Ikeuchi M. Mabuchi N. Otaka A. Tamamura H. Ohno M. Fujii N. Matsuoka M. J. Virol. 2005; 79: 764-770Crossref PubMed Scopus (77) Google Scholar). in the region of in a of the of substitutions on viral we and replication kinetics by in the changes to the for acid and the S138A, in the T-20 resistance mutation N43D background enhanced replication kinetics of the as in Fig. However, in the background the S138A to of as with (Fig. substitutions also replication the substitution show and replication kinetics of the HIV-1 also (supplemental Fig. of of virus in the cells (supplemental Fig. with (supplemental Fig. and replication kinetics (Fig. These results suggest that substitutions at are to in the of T-20 the emergence of N43D of acid with the hydrophobic by and in the The mutation from to and help to the with the of the HIV-1 fusion inhibitors (Fig. hydrophobic substitutions such as are to with efficient of the N-HR and C-HR of at this region of the also the hydrophobic and result in with the and and 1). Based on studies Wilson K.L. Seedorff J.E. D. J. Davison D.K. Jin L. Stanfield-Oakley S.A. Mosier S.M. Melby Cammack N. Greenberg M.L. J.J. 2008; PubMed Scopus Google Scholar, and N. in we that the T-20 resistance N43D mutation should interactions between helices in the 6-helix bundle. of N-HR is to of the C-HR of another in the 6-helix bundle. We that this in and of to the formation of the 6-helix bundle in a that results in of fusion and replication of the hydrophobic interactions by of the S138A mutation should help the of the N43D In this study we demonstrate that by a secondary resistance mutation into the sequence of inhibitors such as C34 and T-20, we can replication of wild-type and of fusion HIV-1. circular dichroism analysis revealed that fusion inhibitors that secondary resistance mutations can form 6-helix with N-HR that primary resistance mutations for T-20 resistance. approach has been for the of short hairpin that inhibit HIV-1 replication H. M. M. T. J. Virol. 2006; 80: PubMed Scopus Google Scholar). The with mutations that resistance to the effectively of resistant HIV-1 wild-type HIV-1. it is possible to from the resistance and it to design peptides in the of that preempt the viral escape mechanism and resistant Moreover, this should result in more that be during of the peptide we A. Nakamura M. Nameki D. Kodama E. Uchiyama S. Nakamura S. Nakano H. Tamamura H. Kobayashi Y. Matsuoka M. Fujii N. Angew. Chem. Int. Ed. Engl. 2002; 41: 2937-2940Crossref PubMed Google Scholar, and M. Int. J. Scholar, S. S. H. K. M. Ohno H. K. Y. Kodama E. Matsuoka M. Fujii N. J. Med. Chem. 2008; PubMed Scopus Google Scholar) and J.J. Wilson K.L. Davison D.K. Freel S.A. Seedorff J.E. Wring S.A. Tvermoes N.A. Matthews T.J. Greenberg M.L. Delmedico M.K. Proc. Natl. Acad. Sci. U. S. A. 2007; 104: 12772-12777Crossref PubMed Scopus (219) Google Scholar) reported that acid substitutions the of C-HR peptides and increased binding to thus potent This be of the of the recently developed potent peptide A. Nakamura M. Nameki D. Kodama E. Uchiyama S. Nakamura S. Nakano H. Tamamura H. Kobayashi Y. Matsuoka M. Fujii N. Angew. Chem. Int. Ed. Engl. 2002; 41: 2937-2940Crossref PubMed Google Scholar, and M. Int. J. S. S. H. K. M. Ohno H. K. Y. Kodama E. Matsuoka M. Fujii N. J. Med. Chem. 2008; PubMed Scopus Google J.J. Wilson K.L. Davison D.K. Freel S.A. Seedorff J.E. Wring S.A. Tvermoes N.A. Matthews T.J. Greenberg M.L. Delmedico M.K. Proc. Natl. Acad. Sci. U. S. A. 2007; 104: 12772-12777Crossref PubMed Scopus (219) Google that have been reported to inhibit T-20 resistant However, the S138A substitution on T-20 in the study on the as by that binding by the of this region J.J. Wilson K.L. Davison D.K. Freel S.A. Seedorff J.E. Wring S.A. Tvermoes N.A. Matthews T.J. Greenberg M.L. Delmedico M.K. Proc. Natl. Acad. Sci. U. S. A. 2007; 104: 12772-12777Crossref PubMed Scopus (219) Google Scholar, 6Otaka A. Nakamura M. Nameki D. Kodama E. Uchiyama S. Nakamura S. Nakano H. Tamamura H. Kobayashi Y. Matsuoka M. Fujii N. Angew. Chem. Int. Ed. Engl. 2002; 41: 2937-2940Crossref PubMed Google Scholar). approach of substitutions on the of the that in resistant viruses improved the with This approach the of helical stability and help more potent and effective fusion inhibitors for resistant HIV-1 have also been to the of HIV fusion inhibitors. is a peptide that is on the T-20 sequence and has improved binding R. D. J. F. J. Virol. 2007; PubMed Scopus (40) Google Scholar, D. Baldwin C.E. Deng Y. J.P. Lu M. Sanders R.W. Berkhout B. J. Virol. 2008; 82: PubMed Scopus Google Scholar). It changes with T-20 and substitutions to the to acid of and immunodeficiency is another efficient peptide fusion inhibitor that was recently developed and is also modified J. M. J. Virol. PubMed Google substitutions in J.J. Wilson K.L. Davison D.K. Freel S.A. Seedorff J.E. Wring S.A. Tvermoes N.A. Matthews T.J. Greenberg M.L. Delmedico M.K. Proc. Natl. Acad. Sci. U. S. A. 2007; 104: 12772-12777Crossref PubMed Scopus (219) Google Scholar). is an peptide that also suppresses replication of T-20-resistant and it required substitutions in the C34 inhibitor A. Nakamura M. Nameki D. Kodama E. Uchiyama S. Nakamura S. Nakano H. Tamamura H. Kobayashi Y. Matsuoka M. Fujii N. Angew. Chem. Int. Ed. Engl. 2002; 41: 2937-2940Crossref PubMed Google Scholar, and M. Int. J. Scholar). it is possible to the of peptide inhibitors and in in vitro studies that to the design and of improved peptide However, the approach we in the design of the inhibitor is and a of sequence changes with and in the of and It of from the viral drug and the resistance to design improved inhibitors. In we that this approach be to even the interactions helical on is a of the two even more effective peptide inhibitors that can replication of resistant is a in HIV-1 fusion also in of have to multiple into the target and cost. such as peptide S. T. T. S. K. Y. J. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, H. A. N.A. M. S.A. Med. 1998; PubMed Scopus Google and T. M. A. Y. M. M. N. S. S. Chem. 2006; PubMed Scopus Google Scholar) have been used to the cell peptide-based can be an in the and of in vitro it has been that the of a target can be inhibited by peptides that have the acid sequence of a domain is for the In such the peptides as that have to of the peptide of be for the of that for peptide-based drug In this study we designed peptides to T-20-resistant HIV-1 To our this is the of of resistance in drug design and be to a domain of the has been by an α-helical domain peptide T.J. S. G. 2004; PubMed Scopus Google Scholar, K. J. S. J. E. Cell. 2006; Full Text Full Text PDF PubMed Scopus Google Scholar). The into cells and the of in cells in However, during prolonged with such cells resistance to the peptides substitutions in the region in the selection for of HIV-1. can that our of resistance to drug resistance help in the design of peptides that the resistant variants more thus to of peptide-based with