Lamivudine

Classification within Antiretroviral Pharmacology

Lamivudine is classified as a nucleoside reverse transcriptase inhibitor (NRTI). drugbank.compatsnap.comnih.govaidsmap.comguidetopharmacology.org This class of antiretroviral drugs functions by interfering with the crucial step of reverse transcription, a process utilized by retroviruses like HIV and also by the hepatitis B virus to replicate their genetic material. drugbank.compatsnap.comaidsmap.com

Specifically, this compound is an analog of cytidine. wikipedia.orgchemeurope.com Upon entering host cells, this compound undergoes intracellular phosphorylation to become its active metabolite, this compound triphosphate (3TC-TP or L-TP). drugbank.compatsnap.comnih.govontosight.ai This triphosphate form then competes with the naturally occurring substrate, deoxycytidine triphosphate (dCTP), for incorporation into the nascent viral DNA chain by the viral reverse transcriptase enzyme. patsnap.comontosight.ai Once incorporated, this compound triphosphate acts as a chain terminator because it lacks the necessary 3'-hydroxyl group required for the formation of the subsequent phosphodiester bond, effectively halting the elongation of the viral DNA chain. drugbank.compatsnap.comontosight.ai This mechanism disrupts viral DNA synthesis, thereby inhibiting the replication of HIV and HBV. drugbank.compatsnap.comontosight.ai

A notable characteristic of this compound is its selective action against viral enzymes with limited inhibitory effect on host cell DNA polymerases at clinically relevant concentrations. patsnap.comnih.govresearchgate.net This selectivity contributes to a reduction in toxicity compared to some other antiviral therapies. patsnap.comnih.gov this compound is effective against both HIV-1 and HIV-2. wikipedia.org

Historical Context of its Research and Therapeutic Development

The discovery and development of this compound represent a key advancement in the treatment of HIV/AIDS and chronic hepatitis B. This compound, initially known as BCH-189, was invented in 1988 by Bernard Belleau at McGill University and Paul Nguyen-Ba at IAF BioChem International, Inc. laboratories in Montreal. wikipedia.org The biologically active minus enantiomer was isolated in 1989. wikipedia.org Early research, including studies by Yung-Chi Cheng at Yale University, explored its properties and effectiveness, particularly in combination with zidovudine (AZT). wikipedia.orgchemeurope.com It was observed that the combination of this compound and AZT synergistically increased the efficiency of inhibiting the reverse transcriptase enzyme and reduced side effects compared to AZT alone. wikipedia.orgmims.com

This compound was licensed by Glaxo-Wellcome in 1990. tandfonline.com It received approval from the U.S. Food and Drug Administration (FDA) in November 1995 for use in combination with zidovudine for HIV treatment. wikipedia.orgchemeurope.comacs.org Its approval marked it as the fifth antiretroviral drug available and the last NRTI for a period while focus shifted to protease inhibitors. chemeurope.com this compound was subsequently approved for the treatment of chronic hepatitis B virus infection. aidsmap.comwikipedia.orgtandfonline.com

The introduction of this compound significantly impacted HIV treatment by contributing to the development of highly active antiretroviral therapy (HAART), which typically involves the use of a combination of antiretroviral drugs. acs.orgnih.gov This combination approach dramatically improved outcomes for individuals with HIV, transforming it from a rapidly fatal disease into a manageable chronic condition. nih.gov this compound's continued relevance in contemporary HIV therapy is highlighted by its inclusion in various fixed-dose combination regimens, addressing challenges related to treatment complexity and adherence. aidsmap.comnih.gov Research continues to explore its use in novel treatment strategies, including two-drug regimens. nih.govnih.govmdpi.com

While highly effective, the development of resistance, particularly in HBV with the YMDD mutation, has been a notable challenge in the long-term use of this compound. wikipedia.orgchemeurope.com Research into resistance patterns remains an important aspect of understanding and optimizing this compound-containing regimens. chemeurope.comnih.gov

Relevant Research Findings:

Research has demonstrated the potent antiviral efficacy of this compound against diverse HIV strains, with in vitro half-inhibitory concentrations (IC50) ranging from 0.002 to 1.14 μM in infected cell lines. researchgate.netnih.govfrontiersin.org Its IC50 against HBV is reported as 0.1 μM. researchgate.netnih.gov

Studies have investigated the pharmacokinetic properties of this compound. It is rapidly absorbed after oral administration, with maximum serum concentrations typically reached between 0.5 and 1.5 hours. nih.govmims.comnih.gov The dominant elimination half-life in adults is approximately 5–7 hours. wikipedia.orgmims.comnih.gov The absolute bioavailability is around 82% in adults. nih.govmims.comnih.gov

Intracellular Anabolism and Active Metabolite Formation

Upon entering target cells, lamivudine undergoes sequential phosphorylation to form its active 5'-triphosphate metabolite, this compound triphosphate (3TC-TP). drugbank.comfrontiersin.orgfda.gov

Inhibition of Viral Polymerases

The active metabolite, 3TC-TP, exerts its antiviral effect by inhibiting viral polymerases. drugbank.compatsnap.comfda.gov this compound is particularly effective against the reverse transcriptase of HIV and the polymerase of HBV. drugbank.comwikipedia.org A significant advantage of this compound is its selective action against viral enzymes, with relatively weak inhibition of human cellular DNA polymerases (α, β, and γ) and mitochondrial DNA polymerase. nih.govfda.gov

Chain Termination Mechanism of DNA Synthesis

The incorporation of 3TC-TP into the viral DNA chain leads to premature chain termination. drugbank.compatsnap.comfda.gov This occurs because 3TC-TP lacks a 3'-hydroxyl group on its deoxyribose sugar analogue. drugbank.compatsnap.com The absence of this critical hydroxyl group prevents the formation of the 5' to 3' phosphodiester bond required for the addition of subsequent nucleotides, thereby halting the elongation of the viral DNA chain and disrupting viral replication. drugbank.compatsnap.com

The chain termination mechanism is a key aspect of this compound's antiviral activity against both HIV and HBV. patsnap.comnih.gov

Selectivity for Viral Enzymes over Host Polymerases

This compound's antiviral action is mediated by its intracellularly phosphorylated active form, this compound triphosphate (3TC-TP). nih.govpatsnap.com This metabolite acts as a competitive inhibitor of viral reverse transcriptase in HIV and HBV polymerase in HBV. nih.govpatsnap.com The selectivity of 3TC-TP for these viral enzymes is a key aspect of its therapeutic profile, allowing it to inhibit viral replication without causing significant damage to host cells. patsnap.com 3TC-TP competes with the natural substrate, deoxycytidine triphosphate (dCTP), for incorporation into the growing viral DNA chain. patsnap.com Once incorporated, 3TC-TP acts as a chain terminator because it lacks the necessary 3'-hydroxyl group required for the formation of the subsequent phosphodiester bond, thus halting viral DNA synthesis. drugbank.compatsnap.com

This selective inhibition is attributed to differences in the binding affinity and catalytic activity of viral reverse transcriptase/polymerase compared to human DNA polymerases. nih.govpatsnap.com While 3TC-TP effectively competes with dCTP for binding to and incorporation by the viral enzymes, its interaction with host polymerases is significantly less potent at therapeutic concentrations. nih.govresearchgate.netnih.gov

Enantiomeric Specificity in Antiviral Activity Research (L-(-)-Enantiomer)

This compound is administered as the L-(-)-enantiomer of 2',3'-dideoxy-3'-thiacytidine. nih.govbocsci.comresearchgate.net The discovery that L-nucleoside analogs could possess potent antiviral activity was a significant development in antiviral chemotherapy. researchgate.net Natural nucleosides have a D-configuration, and initially, antiviral research focused on D-enantiomers. nih.govnih.govbocsci.com

Research into the enantiomeric specificity of this compound revealed that the L-(-)-enantiomer is the primary active form responsible for its antiviral effects against HIV and HBV. nih.govbocsci.comresearchgate.net The L-configuration contributes to the drug's selective activity. The L-(-)-enantiomer is not primarily recognized as a substrate by human polymerases at biologically relevant concentrations, further enhancing its selectivity for the viral enzymes. nih.govnih.govbocsci.com

Studies comparing the L-(-)-enantiomer and its corresponding D-(+)-enantiomer (part of the initially investigated racemic mixture BCH-189) demonstrated that while both could inhibit HIV reverse transcriptase, the L-(-)-enantiomer showed greater potency and less cytotoxicity. bocsci.compnas.org Specifically, the L-(-)-enantiomer ((-)-3TC-TP) is incorporated much less efficiently by human DNA polymerase gamma compared to the D-(+)-enantiomer ((+)-3TC-TP), resulting in lower mitochondrial toxicity and a wider therapeutic index for the L-form. pnas.org This enantiomeric specificity is a crucial factor in this compound's efficacy and tolerability. nih.govresearchgate.netnih.govbocsci.compnas.org

In Vitro and In Vivo Antiviral Potency Assessments

In vitro studies have demonstrated lamivudine's inhibitory activity against various laboratory strains and clinical isolates of HIV-1 in different cell types, including peripheral blood mononuclear cells (PBMCs), monocyte-derived macrophages, and transformed T-cell lines. nih.goveuropa.eu The concentration required to inhibit viral replication by 50% (IC50 or EC50) can vary depending on the specific virus strain and the host cell type used in the assay. nih.goveuropa.eu For instance, IC50 values against HIV-1 in different cell lines and strains have been reported to range from 0.002 to 1.14 µM. nih.gov Against HBV, the IC50 is approximately 0.1 µM. nih.gov While this compound shows similar activity to emtricitabine in primary cells like PBMCs and monocyte-derived macrophages, its potency can differ in transformed cell lines. nih.gov Notably, in vitro antiviral effects are not always reliable predictors of in vivo clinical activity. nih.gov

In vivo assessments in patients have corroborated this compound's antiviral activity, demonstrating its ability to reduce viral load and improve immunological markers, particularly when used in combination therapy. nih.govaidsmap.com

Research on this compound's Role in Combination Antiretroviral Therapy Regimens

This compound is a cornerstone component in numerous combination antiretroviral therapy (cART) regimens for HIV infection. nih.govnih.govresearchgate.net Its inclusion in multi-drug regimens is based on its potent antiviral activity, favorable safety profile, and ability to complement the activity of other antiretroviral agents. nih.govresearchgate.net

Research has consistently shown that this compound-containing combination therapies are significantly more effective in suppressing HIV viral load and increasing CD4+ cell counts compared to monotherapy. nih.govnih.gov Studies like the CAESAR trial demonstrated a substantial reduction in the rate of disease progression or death when this compound was added to zidovudine-based regimens. nih.gov

This compound is frequently combined with other classes of antiretroviral drugs, including other nucleoside reverse transcriptase inhibitors (NRTIs), non-nucleoside reverse transcriptase inhibitors (NNRTIs), protease inhibitors (PIs), and integrase inhibitors (INSTIs). nih.gov Combinations such as this compound plus zidovudine, or regimens incorporating this compound with protease inhibitors or integrase inhibitors like dolutegravir, have shown promising virological efficacy. nih.govfrontiersin.orgdovepress.com Dual therapy regimens, such as dolutegravir plus this compound, are also being explored and have demonstrated substantial virologic efficacy in studies involving virologically suppressed patients. immunologyresearchjournal.com

The use of this compound in combination therapy also plays a role in managing the development of drug resistance. While the M184V mutation in the reverse transcriptase gene confers high-level resistance to this compound, its presence can reduce viral replicative capacity and, in some cases, resensitize the virus to other NRTIs like zidovudine. nih.govnih.gov

Here is a table summarizing some findings on viral load and CD4+ count changes in studies involving this compound in combination therapy:

Monotherapy Research for Hepatitis B Virus Infection

This compound is also approved for the treatment of chronic HBV infection and has been studied as monotherapy in this context. nih.gov this compound monotherapy can lead to initial suppression of HBV replication and a decrease in HBV DNA levels. eur.nlnatap.org

However, a significant limitation of this compound monotherapy for HBV is the high rate of resistance development, primarily due to mutations in the YMDD motif of the HBV polymerase gene. nih.goveur.nlnatap.orgnih.gov Studies have shown that resistance mutations can emerge relatively quickly, leading to virological breakthrough and loss of response. eur.nlnatap.org The cumulative incidence of YMDD mutations has been estimated to be substantial within the first year of treatment. eur.nl

Research has indicated that the effectiveness of this compound monotherapy for HBV can be influenced by baseline viral load and the patient's immune status. natap.orgnih.gov In HIV/HBV co-infected individuals with low baseline HBV DNA levels (<20,000 IU/ml), this compound-based regimens have shown high HBV suppression rates. nih.gov However, in patients with higher baseline HBV DNA, more potent drugs or combination therapy are often more effective and associated with lower resistance rates. nih.govdovepress.com

Studies evaluating this compound monotherapy in specific populations, such as children with immune-tolerant chronic hepatitis B, have suggested that it may not induce complete or sustained viral control. tandfonline.com

Here is a table summarizing some findings on this compound monotherapy for HBV:

The high rate of resistance with monotherapy has led to this compound being less commonly used as a standalone treatment for chronic HBV in current practice, with preference given to more potent agents or combination therapies, particularly in regions with high rates of resistance. nih.govnih.govelsevier.es

Genotypic Characterization of Resistance Mutations

Lamivudine resistance is primarily conferred by specific amino acid substitutions in the catalytic domain of the viral reverse transcriptase/polymerase.

Structural Basis of Resistance Phenotypes

The amino acid substitutions conferring this compound resistance exert their effects by altering the structure and function of the viral reverse transcriptase/polymerase, particularly around the active site.

Viral Fitness and Replication Capacity of Resistant Strains

The mutations conferring this compound resistance, particularly M184V/I in HIV and rtM204V/I in HBV, often come with a trade-off: reduced viral fitness and replication capacity in the absence of the drug nih.govoup.commdpi.com.

In HIV, the M184V mutation is associated with diminished viral replicative fitness nih.govoup.commdpi.com. This reduction in fitness is attributed to several functional changes in the RT enzyme, including decreased processivity, altered pyrophosphorolysis, and reduced nucleotide primer unblocking nih.govnih.govresearchgate.net. Studies have estimated that the M184V mutation can reduce the replication capacity of HIV strains by approximately 10% or more nih.govresearchgate.net. This reduced fitness can lead to a decrease in viral load in patients harboring the M184V mutation, even if complete viral suppression is not achieved nih.govoup.com. The presence of M184V can also influence the selection and impact of other resistance mutations oup.comoup.com.

The reduced fitness of this compound-resistant strains in the absence of the drug has clinical implications. Discontinuation of this compound therapy in patients with the M184V mutation can lead to a rebound in viral load and the potential re-emergence of wild-type or other fitter resistant strains oup.com. Conversely, continuing this compound therapy, even in the presence of resistance, may offer some clinical benefit by maintaining the less-fit resistant population and potentially preserving susceptibility to other antiretroviral agents oup.commdpi.comnih.govoup.com.

Here are some data tables summarizing key findings related to this compound resistance:

Development of Resistance in Monotherapy vs. Combination Therapy Regimens

The development of resistance to this compound is a well-documented phenomenon, occurring much more frequently when the drug is used as a single agent compared to its use in combination with other antiviral drugs. This difference is attributed to the selective pressure exerted by monotherapy, which readily favors the replication of pre-existing or newly emerging drug-resistant viral variants.

In the context of HIV treatment, this compound monotherapy leads to the rapid selection of resistance-associated mutations, most notably the M184V or M184I substitution in the reverse transcriptase enzyme. These mutations can appear within weeks of initiating monotherapy. nih.govresearchgate.netnih.gov While the M184V mutation confers high-level resistance to this compound, it also has been shown to reduce the replication capacity and processivity of the HIV reverse transcriptase, which can result in a partial suppression of viral load even in the presence of resistance. nih.govresearchgate.netnih.govoup.com However, this partial suppression is generally insufficient for long-term viral control and immune recovery. Studies have shown that continuing this compound monotherapy in the presence of the M184V mutation may still offer some limited clinical benefit compared to complete treatment discontinuation, but it is not a recommended strategy due to the risk of further resistance development and treatment failure. nih.govoup.comnih.gov

Similarly, in the treatment of chronic hepatitis B, this compound monotherapy is associated with a high rate of resistance, with cumulative incidence reaching over 50% after 3 years of treatment. nih.gov Resistance mutations in HBV typically occur within the YMDD motif of the viral polymerase. nih.govnih.gov The high rate of resistance with this compound monotherapy for HBV has led to recommendations against its use as a standalone therapy. Combination therapy with other anti-HBV agents, such as adefovir or tenofovir, has been shown to significantly reduce the incidence of this compound resistance in HBV-infected patients. nih.govmedscape.orgxiahepublishing.com For example, studies have reported a low rate of this compound resistance when combined with adefovir, and combination therapy with this compound and tenofovir has been found to be more effective in preventing resistance mutations compared to this compound alone. medscape.orgxiahepublishing.com While some studies have explored switching to tenofovir monotherapy in patients with pre-existing this compound resistance, the initial use of combination therapy with agents having higher barriers to resistance is the preferred approach to prevent resistance development from the outset. plos.org

The difference in resistance development between monotherapy and combination therapy is a critical principle in antiviral treatment. The data below illustrates the significant disparity in resistance rates observed in studies of this compound used as monotherapy versus in combination regimens for both HIV and HBV.

This table highlights the dramatically higher rates of this compound resistance observed with monotherapy compared to its use within combination regimens, underscoring the importance of multi-drug strategies for durable viral suppression and resistance prevention.

Systemic Disposition and Clearance Mechanisms

Lamivudine is primarily eliminated from the body through renal excretion, with over 70% of an oral dose recovered unchanged in the urine. medsafe.govt.nzmedsinfo.com.auviivhealthcare.com This renal clearance is largely mediated by active organic cationic secretion via transport systems such as OCT2, MATE1, and MATE2-K. nih.govmedsafe.govt.nzviivhealthcare.comtga.gov.au Systemic clearance following single intravenous doses averages 20 to 25 L/h (approximately 0.3 L/h/kg). nih.govscielo.br The plasma elimination half-life of this compound is approximately 5 to 7 hours in healthy or HBV-infected patients. nih.govscielo.brdrugbank.comamazonaws.com Metabolism is a minor route of elimination, with the only known metabolite in humans being the inactive trans-sulfoxide metabolite, which accounts for about 5-10% of the dose excreted in urine. nih.govdrugbank.comamazonaws.compharmgkb.org

Intracellular Pharmacokinetics of Active Metabolites

This compound itself is a prodrug that requires intracellular phosphorylation to its active 5'-triphosphate metabolite, this compound triphosphate (3TC-TP). nih.govscielo.brdrugbank.compharmgkb.orgnih.govfda.gov This process involves a series of phosphorylation steps catalyzed by intracellular kinases. pharmgkb.orgnih.gov 3TC-TP is the active form that inhibits viral reverse transcriptase and terminates viral DNA chain elongation. nih.govscielo.brdrugbank.compharmgkb.orgnih.govfda.gov The intracellular half-life of 3TC-TP is significantly longer than that of the parent compound, ranging from 10.5 to 15.5 hours in HIV-1 infected cell lines and 17 to 19 hours in HBV-infected cell lines. nih.govscielo.br This prolonged intracellular half-life supports less frequent dosing regimens. nih.gov

Population Pharmacokinetic Modeling (NONMEM Analysis)

Population pharmacokinetic (PopPK) modeling using methods like NONMEM has been employed to characterize this compound disposition in various patient populations and identify factors influencing variability. asm.orgcapes.gov.brnih.govnih.govresearchgate.netasm.orgnih.govresearchgate.net

Bioavailability Research and Absorption Kinetics

Table 2: Summary of this compound Oral Absorption Parameters

Distribution into Biological Compartments (e.g., Cerebrospinal Fluid, Seminal Mononuclear Cells, Female Genital Tract)

This compound is widely distributed into total body fluid and extravascular spaces, with a mean apparent volume of distribution of approximately 1.3 L/kg following intravenous administration. nih.govscielo.brdrugbank.comamazonaws.com Protein binding in plasma is low, reported as less than 36%. drugbank.comamazonaws.com

Distribution into certain biological compartments is of particular interest due to their role as viral reservoirs. This compound penetrates the cerebrospinal fluid (CSF), although concentrations are typically lower than in plasma. CSF concentrations have been reported to be 4% to 8% of serum concentrations in adults and 9% to 17% in children, measured 2 to 4 hours after dosing. nih.gov The extent of penetration across the blood-brain barrier is considered low to modest, especially in adults. nih.govnih.gov

This compound has been shown to distribute into seminal fluid and seminal mononuclear cells. amazonaws.comnih.govresearchgate.netasm.orgtandfonline.com Studies have reported high accumulation ratios in seminal plasma, with a median seminal plasma to blood plasma total concentration ratio of 2478% in one study. researchgate.net Another source indicates a semen to plasma ratio of 9.1 (range 2.3-16.1). amazonaws.com this compound has also been shown to have a longer half-life in seminal mononuclear cells compared to peripheral blood mononuclear cells. asm.orgnih.gov

In the female genital tract, this compound also exhibits accumulation. nih.govresearchgate.net Similar to seminal fluid, this compound has been shown to have a longer half-life in the female genital tract. nih.gov The distribution into the female genital tract is considered high among nucleoside analogues. researchgate.net

Table 3: this compound Distribution into Select Biological Compartments

Mitochondrial Toxicity Research

Mitochondrial toxicity is a recognized class effect of nucleoside reverse transcriptase inhibitors (NRTIs), the class to which lamivudine belongs. This toxicity is primarily attributed to the interference of these analogs with mitochondrial DNA (mtDNA) replication. oup.comnatap.org

Genotoxicity and Mutagenicity Studies

Genotoxicity refers to the ability of a chemical agent to damage genetic material, while mutagenicity is the induction of permanent transmissible changes in the amount or structure of the genetic material. Studies have been conducted to assess the genotoxic and mutagenic potential of this compound using various in vitro and in vivo systems.

Reproductive and Developmental Toxicity Research (Animal Models)

Reproductive and developmental toxicity studies in animal models have been conducted to assess the potential effects of this compound exposure during critical periods of development and on fertility. These studies primarily involve rodents and rabbits, utilizing various routes and durations of administration to evaluate outcomes such as embryolethality and effects on reproductive capacity.

Interactions with Other Antiretroviral Agents (e.g., Zidovudine, Dolutegravir, Tenofovir, Emtricitabine)

Lamivudine is frequently used in combination with other antiretroviral agents to achieve synergistic antiviral effects and prevent the development of resistance. However, interactions can still occur.

Interactions with Non-Antiretroviral Agents (e.g., Trimethoprim, Cladribine, Sorbitol)

This compound can interact with certain non-antiretroviral agents, primarily through effects on renal transport and intracellular phosphorylation.

Chromatographic Techniques for Quantification

Chromatographic methods are widely employed for the separation and quantification of lamivudine, often in combination with other drugs. These techniques offer high specificity and sensitivity ijbpas.comjgtps.com.

Spectroscopic Approaches (e.g., UV-Visible Spectrophotometry)

UV-Visible spectrophotometry is a simple, rapid, and economical technique for the quantitative estimation of this compound, particularly in bulk drug and pharmaceutical formulations ijbpas.comasianpubs.orgresearchgate.netsaspublishers.comresearchgate.net. This method relies on the principle of measuring the absorbance of this compound solutions at specific wavelengths in the UV-Vis spectrum.

This compound exhibits maximum absorbance (λmax) around 271-272 nm asianpubs.orgresearchgate.netresearchgate.net. UV-Vis spectrophotometric methods for this compound typically involve dissolving the sample in a suitable solvent, such as water or methanol, and measuring the absorbance at the λmax asianpubs.orgresearchgate.netresearchgate.net. Calibration curves are constructed by plotting absorbance values against known concentrations of this compound, and the concentration of unknown samples is determined from the calibration curve or regression equation asianpubs.orgresearchgate.netresearchgate.net.

Research has demonstrated the applicability of UV-Vis spectrophotometry for this compound analysis. A developed UV spectrophotometric method for this compound in bulk and tablet dosage form used water as a solvent and the Area Under Curve (AUC) method in the wavelength range of 265 nm to 275 nm, with λmax at 271 nm. This method showed linearity in the range of 10-60 μg/ml and good reproducibility researchgate.net. Another study reported a UV spectrophotometric method using methanol as a solvent, measuring absorbance at 272 nm, with a linear range of 2.5-20 µg/mL asianpubs.org. Visible spectrophotometric methods involving complex formation with reagents like methyl red have also been explored for this compound estimation saspublishers.com.

Table 5: Summary of Selected UV-Vis Spectrophotometric Methods for this compound Analysis

Bioanalytical Method Development for Biological Fluids (e.g., Plasma, Urine, Intracellular Samples)

Bioanalytical methods for this compound are essential for pharmacokinetic studies, therapeutic drug monitoring, and understanding the drug's disposition in the body nih.govsciencescholar.usnih.govimpactfactor.orgjneonatalsurg.comjapsonline.comnih.govacs.orgmdpi.com. These methods require high sensitivity and selectivity due to the complex nature of biological matrices and the typically low concentrations of the analyte.

LC-MS/MS is the predominant technique for this compound bioanalysis in biological fluids like plasma and urine due to its inherent sensitivity and specificity, which minimizes matrix interference semanticscholar.orgnih.govsciencescholar.usimpactfactor.orgjneonatalsurg.comjapsonline.commdpi.com. Sample preparation steps, such as protein precipitation, liquid-liquid extraction, or solid-phase extraction, are crucial to isolate this compound from the biological matrix components semanticscholar.orgsciencescholar.usjapsonline.com.

Quantification of intracellular this compound and its active phosphorylated metabolites, particularly this compound triphosphate (this compound-TP), is also critical for understanding the drug's pharmacological activity at the cellular level nih.govnih.gov. Specialized LC-MS/MS methods, often employing anion-exchange chromatography for the charged phosphate metabolites, are developed for the analysis of intracellular samples like peripheral blood mononuclear cells (PBMCs) nih.govnih.gov.

Research has focused on developing and validating sensitive bioanalytical methods. A validated LC-MS/MS method for this compound in human plasma demonstrated a linear range suitable for pharmacokinetic studies sciencescholar.us. Studies on intracellular this compound-TP quantification in PBMCs have utilized LC-MS/MS methods, sometimes coupled with radioimmunoassay, highlighting the complexity and specialized techniques required for intracellular analysis nih.govnih.gov. Method validation for bioanalytical applications adheres to regulatory guidelines to ensure reliability and accuracy semanticscholar.orgnih.govsciencescholar.usacs.orgmdpi.com.

Stability-Indicating Assay Method Development

The development of stability-indicating assay methods (SIAMs) for this compound is essential for monitoring its degradation profile and quantifying the intact drug in the presence of its degradation products, impurities, and excipients. These methods are critical for quality control, stability studies, and ensuring the safety and efficacy of this compound-containing pharmaceutical products throughout their shelf life. According to regulatory guidelines, such as those from the International Conference on Harmonisation (ICH), forced degradation studies are a key component in developing and validating SIAMs.

Forced degradation studies involve subjecting the drug substance or drug product to various stress conditions that are likely to be encountered during manufacturing, storage, and handling. Common stress conditions applied to this compound include exposure to acidic, alkaline, neutral hydrolysis, oxidation, heat (thermal stress), and light (photolytic stress) scholars.directjocpr.comresearchgate.net. The purpose is to generate degradation products that can then be separated and detected by the analytical method, thereby demonstrating its specificity and stability-indicating capability.

Research indicates that this compound exhibits varying degrees of degradation depending on the stress condition. Studies have shown that this compound is particularly susceptible to degradation under acidic, alkaline, and oxidative conditions scholars.directresearchgate.netnih.govnih.gov. Neutral hydrolysis, thermal stress, and photolytic degradation have generally shown less significant degradation of this compound scholars.directresearchgate.netnih.gov.

High-Performance Liquid Chromatography (HPLC) is the most widely used technique for developing stability-indicating assay methods for this compound, often coupled with detectors like Diode Array Detection (DAD) or Mass Spectrometry (MS) scholars.directjocpr.comnih.govopenaccesspub.org. The ability of HPLC to separate the active pharmaceutical ingredient from its related substances and degradation products is paramount for a method to be considered stability-indicating.

Several chromatographic conditions have been reported for the stability-indicating analysis of this compound. Typically, reversed-phase HPLC (RP-HPLC) is employed using C18 stationary phases scholars.directajol.infohumanjournals.comijpsr.info. Mobile phases often consist of mixtures of aqueous buffers (such as phosphate buffer or ammonium acetate buffer at various pH values) and organic modifiers like acetonitrile or methanol, used in isocratic or gradient elution modes scholars.directajol.infohumanjournals.comijpsr.info. Detection is commonly performed using UV detection at wavelengths around 260-280 nm, where this compound has significant absorbance scholars.directajol.infohumanjournals.comijpsr.info.

Examples of reported chromatographic conditions for stability-indicating methods include:

A C18 column (4.6 × 150 mm, 5 μm) with an isocratic mobile phase of acetonitrile and 50 mM phosphate buffer (pH 4) (10:90 v/v), flow rate 1.0 mL/min, and detection at 280 nm scholars.direct.

A C18 column (250 mm × 4.6 mm, 5 µm) with a gradient elution using methanol and a mixture of ammonium dihydrogen phosphate and diammonium hydrogen phosphate buffer (pH 3.9), flow rate 1.0 mL/min, and UV detection at 270 nm for simultaneous determination with tenofovir disoproxil fumarate ajol.info.

A C18 column (250 x 4.6 mm) using a mobile phase of methanol:water (90:10, v/v) at a flow rate of 1.0 mL/min and detection at 271 nm humanjournals.com.

An Inertsil ODS column (4.6 mm × 250 mm, 5 µm) with an isocratic mobile phase of 10 mM Ammonium acetate buffer (pH 3.8):acetonitrile (60:40, v/v), flow rate 1.2 mL/min, and detection at 268 nm for simultaneous determination with zidovudine and nevirapine .

Validation of a stability-indicating method is performed according to guidelines such as ICH Q2(R1). Key validation parameters include specificity (demonstrating separation of the drug from degradation products and excipients), linearity (showing a proportional relationship between concentration and response over a defined range), accuracy (closeness of measured values to true values), precision (reproducibility of the method), limit of detection (LOD), limit of quantification (LOQ), and robustness (insensitivity to small variations in method parameters) scholars.directhumanjournals.comijpsr.info. Forced degradation studies are integral to proving the specificity and stability-indicating power of the method scholars.directjocpr.comajol.infowjpps.com.

Several studies have reported successful development and validation of stability-indicating RP-HPLC methods for this compound, demonstrating good linearity, accuracy, and precision within specified concentration ranges scholars.directhumanjournals.comijpsr.info. The ability of these methods to resolve this compound peaks from those of its degradation products confirms their suitability for stability testing scholars.directjocpr.comajol.infowjpps.com.

Detailed research findings from forced degradation studies provide insights into this compound's stability profile. For instance, one study reported the following approximate degradation percentages under extensive stress testing conditions:

Other studies also confirm significant degradation under acidic, alkaline, and oxidative conditions, while showing relative stability to heat and light researchgate.netnih.gov. The degradation products formed under these conditions can be further characterized using techniques like LC-MS to elucidate degradation pathways researchgate.netnih.gov.

The development and validation of these stability-indicating methods are crucial steps in ensuring the quality and stability of this compound, enabling accurate monitoring of the drug substance and drug product over time and under various environmental influences.

Influence on Host Immune Responses in Viral Infections

Lamivudine's impact on host immune responses is primarily considered to be indirect, stemming from its ability to reduce viral load. By suppressing viral replication, this compound can facilitate the restoration of certain immune functions that were previously suppressed by high viral burdens. In patients with chronic HBV infection, reduction of viral and antigen load through this compound treatment has been shown to enhance the vigor of the T cell response to HBV core antigen (HBcAg) and hepatitis B e antigen (HBeAg). This enhancement of the CD4-mediated response to HBV nucleocapsid antigens was observed relatively quickly after initiating this compound treatment, concomitant with a rapid decline in viremia. Furthermore, this compound treatment was associated with an increase in circulating HBeAg-reactive T cells in a significant proportion of patients. Interestingly, the effects were not limited to HBV-specific T cells, as this compound also enhanced responses to mitogens and recall antigens, suggesting a broader impact on T cell function. This restoration of T cell responsiveness highlights the importance of viral load in the pathogenesis of T cell hyporesponsiveness in chronic hepatitis B.

Studies in children with chronic HBV infection treated with this compound have also shown a brisk suppression of serum HBV DNA loads. oup.com High pre-therapy alanine aminotransferase (ALT) levels, which are considered surrogate markers of host immune responses, were associated with HBeAg clearance in these children. oup.com This suggests that a more robust host immune response might enhance early clearance of the virus. oup.com

In the context of HIV infection, this compound, as part of combination antiretroviral therapy (ART), contributes to increasing CD4+ T cell counts, which are crucial for fighting off infections and improving immune system function. nih.goviapac.org

Role in Modulating Cellular Pathways (e.g., Inflammation, Cell Death)

Research suggests that this compound may have roles in modulating cellular pathways beyond its direct antiviral activity, including those involved in inflammation and cell death.

Studies have explored the potential of this compound to influence apoptosis (programmed cell death). One study indicated that regimens including this compound were associated with persistent T cell apoptosis, particularly following CD95 ligation, and that this compound stimulated in vitro CD95-induced apoptosis and caspase activation in pre-activated T lymphocytes from healthy donors. nih.gov This suggests a potential immunomodulatory effect of this compound contributing to increased levels of T cell apoptosis under highly active antiretroviral therapy (HAART). nih.gov

This compound has also been investigated for its effects on inflammation. Research into age-related disorders suggests that this compound can decrease the interferon response and the senescence-associated secretory phenotype (SASP), which are characteristics of senescent cells that promote inflammation. brown.edufiercebiotech.com In mouse models, this compound treatment reduced evidence of both the interferon response and inflammation. brown.edufiercebiotech.com Additionally, this compound has been shown to inhibit Alu RNA-induced retinal pigment epithelium (RPE) inflammation by reducing the expression of pro-inflammatory cytokines like IL-18 and IL-1β. researchgate.netarvojournals.org this compound is known to inhibit the NLRP3 inflammasome, a key component in inflammatory pathways. researchgate.netarvojournals.org

Furthermore, this compound has been shown to modulate the expression of genes related to neurological impairment and inflammation pathways in a mouse model of Down syndrome, downregulating genes involved in Alzheimer's neuropathology and neuroinflammation. frontiersin.org

Co-infection Dynamics (e.g., HIV/HBV Co-infection)

Co-infection with HIV and HBV is common due to shared transmission routes and presents significant clinical challenges. natap.orgircmj.com this compound is active against both viruses, making it a crucial component of treatment regimens for co-infected individuals. nih.govdrugbank.comiapac.org

In HIV/HBV co-infected patients, the effect of this compound on HBV replication can depend on the host immune status, particularly the CD4 cell count. natap.orgnih.gov Hepatitis B may be considered an opportunistic infection in this context, with a CD4 cell-dependent response to this compound therapy observed in some studies. natap.orgnih.gov HIV co-infection is associated with a reduced frequency of spontaneous recovery from HBV infection, higher levels of HBV replication, and an increased risk of cirrhosis. natap.org Studies have shown that HIV co-infection can lead to a poorer response to interferon-alpha therapy and more frequent HBV reactivations. natap.org

While this compound monotherapy can suppress HBV replication in co-infected patients, the emergence of this compound-resistant HBV can occur rapidly. natap.orgnih.gov Studies have shown a high prevalence of HBV drug-resistant mutations, particularly M204I and L180M, in HBV/HIV co-infected patients on ART regimens including this compound. nih.govkarger.com Combination therapy, such as this compound plus Tenofovir, is recommended for HIV/HBV co-infection due to a superior resistance profile compared to this compound monotherapy. d-nb.inforesearchgate.net

Data from studies on HIV/HBV co-infection have shown that while combination therapy including this compound can lead to higher rates of undetectable HBV DNA compared to this compound monotherapy over time, the impact on immune recovery (CD4 count) may be similar between this compound- and Tenofovir-treated participants in some cohorts. d-nb.inforesearchgate.netmdpi.com

Research on the Absence of Direct Immunomodulatory Effects (e.g., vs. Interferon-alpha)

While this compound can indirectly influence immune responses by reducing viral load, research has also highlighted the absence of direct immunomodulatory effects when compared to agents like interferon-alpha (IFN-α). scielo.brelsevier.eseuropa.eu

Interferon-alpha is known to exert its therapeutic effects through stimulation of the host immune system and has direct antiviral effects. europa.eumednexus.orgresearchgate.net In contrast, this compound's primary mechanism is the inhibition of viral reverse transcriptase, blocking viral DNA synthesis. nih.govdrugbank.comeuropa.euaidsmap.com Studies comparing this compound and interferon-alpha in chronic hepatitis B treatment have noted that unlike interferon-alpha, this compound does not have a direct immunomodulatory effect. scielo.brelsevier.es This characteristic makes this compound a potentially suitable option for patients where immunomodulation is undesirable, such as renal transplant patients with HBV infection, as it was not associated with rejection episodes in one study. scielo.br

Mathematical models characterizing the long-term dynamics of HBV markers during treatment have also indicated that while Pegylated interferon (Peg-IFN) has a significant immunomodulatory effect leading to enhanced loss rates of infected cells, this compound primarily has a larger effect in blocking viral production. nih.govresearchgate.net

Despite the lack of direct immunomodulatory effects, the reduction in viral load achieved by this compound can indirectly restore or improve host immune responses that were suppressed by high viral replication. oup.com

Neuroprotective Mechanisms and Applications

Research suggests that lamivudine may exert neuroprotective effects through several mechanisms, primarily involving the inhibition of retrotransposon activity and subsequent downstream effects on neuroinflammation and cellular senescence. alzdiscovery.orgbrown.eduuthscsa.edu

Research in Metabolic Disorders (e.g., Diabetes, Insulin Resistance)

Emerging research suggests that this compound may have potential applications in the context of metabolic disorders, particularly type 2 diabetes and insulin resistance. alzdiscovery.orgbusinesswire.comnih.gov This potential is linked to its effects on inflammasome activation. alzdiscovery.orgbusinesswire.comnih.gov

Cancer Research Perspectives

Research into the potential repurposing of this compound, a nucleoside reverse transcriptase inhibitor primarily known for its activity against HIV and Hepatitis B virus, has explored its possible applications in oncology. Studies suggest that this compound may possess anti-cancer properties through various mechanisms, including sensitizing cancer cells to chemotherapy and potentially having direct effects on neoplastic processes. nih.govnih.gov

One area of investigation involves the observation that certain cancers exhibit high levels of the reverse transcriptase enzyme. massgeneral.org This has led researchers to hypothesize that inhibiting reverse transcriptase activity might be a viable strategy in cancer treatment. Preclinical studies have indicated that colorectal cancer cells, for instance, are sensitive to this compound, showing reduced ability to move and an induction of inflammatory responses within the tumor cells. bjmo.becontagionlive.comharvard.edu this compound has been shown to induce DNA damage and interferon responses in preclinical models of colorectal cancer, suggesting a drug-triggered inflammatory response in these cells. bjmo.beharvard.edu

Clinical trials are underway to evaluate this compound's effectiveness in various cancer types. An active Phase 2 trial is investigating this compound in combination with chemoimmunotherapy for the treatment of extensive stage small cell lung cancer, based on the premise that this compound might reduce the ability of tumors to develop drug resistance. cancer.govroswellpark.org Another active Phase 1/Phase 2 trial is testing this compound with standard of care anti-PD-L1 blockade for patients with relapsed or refractory unresectable solid tumors that have progressed on prior anti-PD-(L)1 therapy. cancer.govcancer.gov Research in mice suggests this compound may help the immune system eliminate solid tumors. cancer.gov

A Phase 2 study specifically investigated this compound in patients with p53 mutant metastatic colorectal cancer who had progressed on prior systemic therapy. nih.gov This single-arm study enrolled 32 patients. massgeneral.orgbjmo.benih.gov The study design involved two stages, with an initial group of 9 patients receiving this compound at 150 mg orally twice daily, and subsequent patients (10-32) receiving a higher dose of 600 mg orally twice daily. nih.gov Tumor assessments were conducted every 8 weeks. nih.gov Findings from this trial indicated that this compound stopped disease progression in a proportion of patients with heavily pre-treated metastatic colorectal cancer. massgeneral.orgbjmo.becontagionlive.comharvard.edu Specifically, 9 out of 32 patients (28%) showed disease stability or a mixed response at the end of the trial. massgeneral.orgharvard.edu While tumor shrinkage was not observed, these results were considered encouraging and provided evidence for repurposing an HIV drug as an anti-cancer therapy in metastatic cancer patients. massgeneral.orgbjmo.beharvard.edu

Beyond inhibiting reverse transcriptase, other potential mechanisms for this compound's anti-cancer effects are being explored. This compound may induce necroptosis, a form of programmed cell death, which could be a therapeutic strategy for treatment-resistant cancers. acs.org It may also disrupt DNA repair mechanisms, increasing cancer cell sensitivity to genotoxic stress and promoting apoptosis or senescence. acs.org Furthermore, the impact of this compound on the STING pathway, which triggers an immune response upon detecting cytosolic DNA, is being investigated as a way to enhance the immune system's ability to eliminate cancer cells. acs.org Interference with telomerase reverse transcriptase (TERT), an enzyme often overexpressed in cancers, is another proposed mechanism by which this compound might limit cancer cell survival. acs.orgalzdiscovery.org

Prophylactic use of this compound has also been examined in the context of preventing Hepatitis B virus reactivation in cancer patients undergoing chemotherapy, which can be a life-threatening complication. nih.govnih.gov A meta-analysis in breast cancer patients with positive Hepatitis B surface antigen undergoing chemotherapy showed that prophylactic this compound reduced the rates of HBV reactivation, incidence of hepatitis, and chemotherapy disruption related to HBV reactivation compared to a control group. nih.gov

The exploration of this compound-loaded polymeric nanoparticles is also underway to potentially improve therapeutic efficacy through enhanced bioavailability, stability, and targeted delivery. acs.org Studies suggest that these nanoparticles may exhibit dose-dependent cytotoxic effects and high anticancer activity in preclinical models, such as breast and lung cancer. acs.org

Here is a summary of selected clinical trial findings for this compound in cancer research:

Note: Data for active trials may be preliminary or not yet publicly available in detail.

Further research, including larger Phase 3 studies, is needed to fully understand the potential of this compound as an anti-cancer therapy, both as a single agent and in combination with other treatments. contagionlive.com

Crystal Structure Analysis of Viral Polymerases with Lamivudine Analogues

Crystal structure analysis of viral polymerases, particularly HIV-1 RT, in complex with DNA template-primer and nucleotide analogs, has been instrumental in visualizing the binding site and the interactions between the enzyme, nucleic acid, and the inhibitor. While crystal structures of HIV-1 RT with DNA have been determined, including complexes with DNA/DNA template-primers, direct crystal structures of HIV-1 RT in complex with a template-primer and 3TCTP have been sought to fully elucidate the structural details of inhibition and resistance. pnas.orgnih.gov

Studies involving crystal structures of HIV-1 RT containing resistance mutations, such as M184V, in the presence and absence of DNA template-primer have provided insights into the structural basis of resistance. pnas.orgnih.govasm.org Comparison of wild-type and mutant RT structures reveals changes in the dNTP-binding site and potential repositioning of the template-primer in the mutant enzymes. pnas.orgnih.gov

Computational Modeling of Ligand-Enzyme Binding (e.g., HBV Polymerase Homology Models)

Due to the challenges in obtaining crystal structures for all relevant enzyme-ligand complexes, particularly for HBV polymerase which is part of a larger protein and lacks a readily available standalone crystal structure, computational modeling has played a vital role. Homology models of the catalytic core of HBV polymerase have been constructed based on the known crystal structures of retroviral reverse transcriptases, such as HIV-1 RT, leveraging the sequence homology in key regions like the active site. researchgate.netmdpi.comasm.orgresearchgate.net

Molecular modeling studies using these HBV polymerase homology models have been used to investigate the binding interactions of this compound triphosphate (3TCTP) with the enzyme. researchgate.netmdpi.com These studies suggest that 3TCTP interacts with the HBV DNA polymerase active site, inducing conformational changes in nearby residues, such as M204 (equivalent to M184 in HIV-1 RT), which are crucial for inhibition. xiahepublishing.com Computational approaches like molecular docking predict the preferred binding modes and affinities of this compound and its analogs to the enzyme active site. researchgate.netresearchgate.net Molecular dynamics simulations provide a more dynamic view, allowing researchers to observe the conformational adaptations of both the ligand and the protein upon binding and to estimate binding free energies. researchgate.netukzn.ac.zaacs.orgrsc.org

Predictive Modeling of Resistance Mutations and Conformational Changes

Computational modeling is extensively used to understand the structural basis of this compound resistance mutations and to predict their impact on enzyme-ligand interactions and conformational dynamics. The primary this compound resistance mutations in both HIV-1 RT and HBV polymerase occur at a conserved methionine residue within the YMDD motif (M184 in HIV-1 RT and M204/M552 in HBV polymerase, depending on numbering convention). pnas.orgmdpi.comasm.orgmicrobiologyresearch.orgnih.gov Mutations at this position, typically to valine (V) or isoleucine (I), confer high-level resistance. pnas.orgasm.orgmicrobiologyresearch.org

Molecular modeling studies, including molecular dynamics simulations, have demonstrated that these mutations, particularly M184V in HIV-1 RT and M204V/I (or M552V/I) in HBV polymerase, lead to steric hindrance between the bulkier side chains of valine or isoleucine and the oxathiolane ring of 3TCTP. pnas.orgnih.govresearchgate.netmdpi.comresearchgate.netukzn.ac.zarsc.org This steric conflict perturbs inhibitor binding, significantly reducing the binding affinity of 3TCTP compared to the wild-type enzyme. researchgate.netukzn.ac.zarsc.org

Predictive modeling can also explore the effects of compensatory mutations, such as L180M and V173L in HBV polymerase, which often emerge alongside the primary resistance mutations and can restore viral replication fitness. asm.orgnih.govasm.org Molecular models suggest that these compensatory mutations, while not directly affecting this compound binding, may enhance polymerization by repositioning the template strand or affecting other residues involved in the catalytic process. asm.org

Computational approaches are also being explored for predicting the emergence of resistance mutations and understanding the dynamics of viral populations under selective pressure from this compound therapy. asm.orgnih.govelifesciences.org

Here is a table summarizing some key findings from structural and modeling studies: