(Yksi tällainen tekijä TRIM28 (KAP1, TIFB) on integraasin estäjä funktioltaan. tästä erikseen edellä).
HIV-1 integraasin(IN) esto tarkoitaa käytännössä sitä, että estetään virusta saamasta oma provirusmateriaalinsa integroiduksi ihmisen genomiin.
On kehitelty viruksen intrgoitumisen estämiseksi lääkkeitä, INSTI- ryhmä. ( Integration strand trnasfer inhibitors). niistä täässä alla artikkeli vuodelta 2017. otaten huomioon että HIV-1 virus menee hyvin varhain neurologiseen kudokseen ja aivoon ja suoritaa integraatiota, integraasin eston tulisi tapahtua varhain.
HIV drug resistance against strand transfer integrase inhibitors
Thibault MespledeEmail authorView ORCID ID profile and
Mark A. Wainberg^
Thibault MespledeEmail authorView ORCID ID profile and
Mark A. Wainberg^
© The Author(s) 2017
Accepted: 30 May 2017
Published: 5 June 2017
Integrase strand transfer inhibitors (INSTIs) are the newest class of antiretroviral drugs to be approved for treatment and act by inhibiting the essential HIV protein integrase from inserting the viral DNA genome into the host cell’s chromatin. Three drugs of this class are currently approved for use in HIV-positive individuals: raltegravir (RAL), elvitegravir (EVG), and dolutegravir (DTG), while cabotegravir (CAB) and bictegravir (BIC) are currently in clinical trials. RAL and EVG have been successful in clinical settings but have relatively low genetic barriers to resistance. Furthermore, they share a high degree of cross-resistance, which necessitated the development of so-called second-generation drugs of this class (DTG, CAB, and BIC) that could retain activity against these resistant variants. In vitro selection experiments have been instrumental to the clinical development of INSTIs, however they cannot completely recapitulate the situation in an HIV-positive individual. This review summarizes and compares all the currently available information as it pertains to both in vitro and in vivo selections with all five INSTIs, and the measured fold-changes in resistance of resistant variants in in vitro assays. While the selection of resistance substitutions in response to RAL and EVG bears high similarity in patients as compared to laboratory studies, there is less concurrence regarding the “second-generation” drugs of this class. This highlights the unpredictability of HIV resistance to these inhibitors, which is of concern as CAB and BIC proceed in their clinical development.
Since the beginning of the pandemic, HIV/AIDS has claimed the lives of over 35 million people, and approximately 35 million individuals are currently infected . Highly active antiretroviral therapy (HAART) has transformed a positive HIV diagnosis from a former death sentence into a chronic, manageable disease. However, no cure yet exists for HIV and patients must remain on therapy for the entirety of their lives which makes the development of drug resistance in the virus a real concern. In fact, drug resistance has been documented for every currently available drug class in patients . This makes the continued study of the mechanisms of HIV drug resistance and novel therapeutics a top priority for HIV scientists worldwide.
The reverse transcriptase (RT) enzyme of HIV is highly error-prone, introducing mutations into the genome at a rate of 1.4 × 10−5 mutation per base pair, per replication cycle . This high mutation rate allows for the generation of multiple different viruses within an infected individual, sometimes referred to as “quasi-species.” If one of these quasi-species has a mutation that provides a selective advantage for replication in the presence of antiretrovirals (ARVs), it will out-compete other viral forms to become the dominant species .
The integrase (IN) enzyme catalyses the insertion of the viral DNA (vDNA) into the host’s genome through two catalytic actions: 3′ processing and strand transfer. In the cytoplasm, IN self-associates into tetramers on the newly reverse transcribed vDNA, where it catalyzes the removal of the last two nucleotides from the 3′ ends of both strands . In addition, IN can spontaneously form larger multimers that are stabilized by the addition of allosteric integrase inhibitors, and reciprocally destabilized in the presence of DNA [6, 7, 8, 9, 10]. After nuclear translocation, IN associates with lens epithelium-derived growth factor (LEDGF)/p75 and is directed to sites of open chromatin, where it will initiate strand transfer, i.e. the nucleophilic attack of the 3′ hydroxyl groups on the viral DNA on the nucleotide backbone of the host DNA. The integration process is completed by host gap-repair machinery, resulting in a 5 base-pair repeat that flanks each end of the viral DNA .
The integrase strand transfer inhibitor (INSTI) class of antiretroviral drugs is the latest to be approved for treatment of HIV-positive individuals. As their name suggest, INSTIs inhibit the second step catalyzed by IN, i.e. strand transfer, through competitive binding to the enzyme’s active site. INSTIs not only displace the 3′ end of the vDNA from the active site, but also chelate the divalent cation (Mg2+ or Mn2+) that is required for IN enzymatic activity . There are currently three INSTIs approved for the treatment of HIV infection: raltegravir (RAL), elvitegravir (EVG), and dolutegravir (DTG) . Cabotegravir (CAB) and bictegravir (BIC) are newer INSTIs currently in clinical trials [14,15)
Although highly efficacious in the management of HIV, both RAL and EVG are susceptible to virological failure through the development of resistance mutations. What is more, most of the changes that cause resistance to RAL also cause resistance to EVG, and vice versa . This is, however, not the case with DTG. Not only does DTG appear to have a higher genetic barrier to resistance than either of the other two drugs, it has not yet been shown to definitively select for any resistance-associated changes in treatment-naïve patients . Although two reports of potential emergence of resistance in individuals treated with DTG in first line therapy recently appeared, baseline IN was not sequenced in one of these cases, nor did the supposed-emergent mutation lead to persistent virological failure while DTG was still being used together with an optimized background regimen containing rilpivirine (RPV), an NNRTI with a modest genetic barrier to resistance . Specifically, initial TDF/FTC/DTG treatment was supplemented with ritonavir-boosted darunavir following failure; the latter drug was subsequently substituted with RPV for reason of diffuse erythoderma. The second case reported transient emergence of a T97A substitution that did not confer any resistance on its own against DTG in vitro and was not observed at subsequent time points . Although it cannot be excluded that unambiguously documented cases of emergent resistance mutations against first-line DTG will eventually be reported, it is expected that this will be rare. This is supported by the fact that despite dolutegravir being used by tens of thousands treatment-naïve individuals in Europe and the USA, the abovementioned two cases are the only known reports of potential primary de novo resistance against this drug. There have also been rare cases of treatment failure with resistance mutations in treatment-experienced but INSTI-naïve patients, and, in this setting, DTG has most often selected for the novel resistance substitution R263K . Other substitutions at residues E92, Q148 and N155, have been reported when DTG monotherapy was used in treatment-experienced patients.
Primary resistance substitutions arise first in response to INSTI drug pressure and cause a decrease in susceptibility at the expense of viral fitness, most often through alterations to the enzyme’s active site where the inhibitors bind [16, 21]. Secondary resistance substitutions arise after continued drug pressure and usually act to alleviate the negative effects of primary mutations, and may also increase levels of INSTI resistance [22, 23]. Some of these secondary changes are specific to a certain primary resistance pathway, but many may be selected after several different primary mutations.
Pre-clinical and in vitro studies have been instrumental in the evaluation of novel therapeutic agents for the treatment of HIV infection, however they do not always accurately predict clinical outcomes for patients. Laboratory viral strains and cell lines, although excellent scientific tools, can never recapitulate in vivo human infections with 100% accuracy. In this review, we compare both the in vitro selection and antiviral activity reported for drugs of the INSTI class with the analogous data available from treated patients to assess the predictive power of in vitro studies for INSTI clinical outcomes.
In 2004 a group of researchers at Merck & Co. reported on the efficacy of the diketo acid (DKA)-based lead compound L-870812 against simian immunodeficiency virus (SIV) in infected rhesus macaques . This led to the approval of the first INSTI, raltegravir, in 2007 for treatment-experienced AIDS patients with multidrug resistance, and two years later for treatment-naïve individuals as well [25, 26]. In the 10 years since its first approval, RAL has been shown to be well tolerated in the vast majority of patients, although it is does require twice daily dosing. It displays a modest genetic barrier to resistance, with the most common mutational pathways consisting of changes at positions Y143, Q148, and N155 .......( more information in the link)
EVG is a monoketo acid derivative that also demonstrated high specificity for inhibition of HIV IN strand transfer reactions . EVG was developed by Gilead Sciences and approved for use in HIV infected individuals in 2012 . Because EVG is processed by the cytochrome p450 enzyme CYP3A4/5, it needs to be co-formulated with cobicistat to boost plasma concentrations. This permits once daily dosing of EVG .It is evident from both Tables 3.........( More information in the link)
The relatively low genetic barrier and high degree of cross-resistance among the so called “first-generation” INSTIs RAL and EVG spurred research into the chase for “second-generation” drugs of this class, aimed at retaining efficacy against RAL/EVG resistant variants. There have been four candidate second-generation INSTIs to date. DTG, manufactured by ViiV-Healthcare and GlaxoSmithKline, was approved in 2013 for both treatment-naïve and—experienced patients and is the only second-generation INSTI to be approved to date . MK-2048 showed potent activity against most RAL/EVG resistant variants and did not select for the same substitutions in tissue culture studies but its clinical development was halted due to poor pharmacokinetics. Both CAB and BIC are promising and both are currently in advanced clinical trials [15, 19, 50, 80].
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There are fewer reports on the resistance patterns of CAB, a novel INSTI under development at GlaxoSmithKline. CAB was developed concomitantly with DTG and shares most of its structure; it has the potential to be formulated as a long acting injectable for both pre-exposure prophylaxis and treatment of HIV infection . In the LATTE clinical trial, one patient in the CAB arm did develop a mutation in the Q148 pathway, which suggests that this second-generation INSTI may select for the same mutations as RAL and EVG . In in vitro selection studies, CAB has selected for changes at positions 146 and 153 that could also be selected in the presence of EVG and DTG, respectively (Table 4).
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