Vincristine

Oxidation of Vinblastine to Vincristine

Reaction Conditions and Reagents

The oxidation of vinblastine (VLB) to this compound represents a semi-synthetic pathway leveraging the structural similarity between the two alkaloids. This method employs an acidic ferrous perchlorate-hydrogen peroxide system under rigorously controlled conditions. Key parameters include:

• Temperature : -20°C to -40°C to minimize side reactions.
• Solvent : Acetonitrile, chosen for its low coordinating power with iron and inertness toward reactants.
• Oxidizing Agents : Ferrous perchlorate hexahydrate and 30% hydrogen peroxide, activated by perchloric or acetic acid.

Procedural Details from US4303584A

A representative procedure involves dissolving vinblastine sulfate (142 mg) in acetonitrile, mixing with 70% perchloric acid, and adding the solution to a chilled (-20°C) ferrous perchlorate suspension. Hydrogen peroxide in acetonitrile is then introduced over 25 minutes, maintaining the temperature at -20°C. Post-reaction quenching with sodium bisulfite and extraction with methylene dichloride yields crude this compound, which is purified via preparative thin-layer chromatography (TLC) using silica plates. This method achieves yields up to 35%, a significant improvement over traditional chromic acid oxidations.

Table 1: Key Parameters in Vinblastine Oxidation

Purification Techniques

Post-oxidation purification involves sequential washes with ammonium hydroxide, phosphate buffer (pH 7), and saturated sodium chloride. Chromatography on silica or alumina, followed by crystallization, ensures pharmaceutical-grade purity.

Total Synthesis of this compound

Stereoselective Coupling Strategy

The 2004 total synthesis by Fukuyama et al. hinges on coupling demethylvindoline with an eleven-membered carbomethoxyverbanamine precursor. Demethylvindoline is synthesized via oxidation of 17-hydroxy-11-methoxytabersonine, followed by regioselective acetylation using a mixed anhydride method.

Critical Synthetic Steps

• Oxidation and Acetylation : 17-Hydroxy-11-methoxytabersonine undergoes oxidation to form demethylvindoline, which is acetylated at the C17 position.
• Coupling Reaction : Demethylvindoline reacts with the carbomethoxyverbanamine precursor, achieving stereochemical control at C18′.
• Piperidine Ring Formation : Sequential deprotection and intramolecular cyclization yield the this compound skeleton.

Table 2: Total Synthesis Yield and Key Steps

Alternative Synthetic Routes

1,4-Dihydropyridine-Mediated Synthesis

US5047528A discloses a method using 1,4-dihydropyridine compounds to reduce vindoline-carbomethoxyvelbanamine intermediates. For example, sodium borohydride reduction of a dihydropyridine derivative yields this compound alongside by-products like 3',4'-dehydrovinblastine (17%) and leurosine (9%).

By-Product Analysis

The reduction process generates multiple alkaloids, necessitating rigorous chromatographic separation. Reverse-phase HPLC quantifies yields, with this compound constituting 23% of the crude product.

Table 3: By-Products in Alternative Synthesis

Comparative Analysis of Preparation Methods

Pharmaceutical Formulation

DBL™ this compound Sulfate Injection exemplifies the final preparation, containing 1 mg/mL this compound sulfate and 100 mg/mL mannitol in water. The formulation avoids preservatives, ensuring compatibility with intravenous administration.

Stability Considerations

• Storage : 2–8°C, protected from light.
• Administration : Diluted in 0.9% sodium chloride or 5% dextrose.

Vincristine undergoes various chemical reactions, including oxidation, reduction, and substitution . Common reagents used in these reactions include oxidizing agents, reducing agents, and nucleophiles . The major products formed from these reactions depend on the specific conditions and reagents used . For example, oxidation of this compound can lead to the formation of different oxidized derivatives, while reduction can yield reduced forms of the compound .

Clinical Applications

Vincristine is approved for treating various malignancies, including:

• Acute Lymphoblastic Leukemia (ALL)
• Hodgkin's and Non-Hodgkin Lymphomas
• Neuroblastoma
• Wilms Tumor
• Rhabdomyosarcoma
• Kaposi Sarcoma

FDA-Approved Indications

Off-Label Uses

In addition to its approved indications, this compound is used off-label for:

• Central Nervous System (CNS) tumors
• Ewing Sarcoma
• Medulloblastoma
• Bladder Cancer
• Ovarian Cancer

Combination Therapies

This compound is often used in combination with other chemotherapeutic agents to enhance efficacy while minimizing adverse effects. Notable combination regimens include:

• CHOP : Cyclophosphamide, Doxorubicin, this compound, Prednisolone
• CVP : Cyclophosphamide, this compound, Prednisolone
• CISCA : Cisplatin, Doxorubicin, Vinblastine, Bleomycin

Case Studies and Clinical Trials

Numerous studies underscore this compound's effectiveness across different cancer types. A notable trial reported that this compound administered weekly to children with advanced cancer resulted in a 68% objective tumor response rate across various malignancies, including ALL and Hodgkin's disease .

Clinical Trial Insights

Pharmacokinetics and Challenges

This compound's pharmacokinetic profile reveals rapid distribution and significant protein binding (approximately 75%). However, its clinical use is limited by neurotoxicity and other side effects such as alopecia and constipation. Recent advancements focus on improving its delivery through nanotechnology-based formulations to enhance targeting and reduce toxicity .

Emerging Trends

Research continues to explore this compound's role in combination therapies and novel formulations. For instance, liposomal formulations like Marqibo have been developed to prolong circulation time and improve dosing efficacy for patients with relapsed ALL . Additionally, ongoing studies are investigating its use in treating solid tumors and enhancing its therapeutic index through innovative drug delivery systems .

Vincristine exerts its effects by binding to tubulin, a protein that is essential for the formation of microtubules . By inhibiting microtubule formation, this compound disrupts the mitotic spindle, leading to cell cycle arrest at the metaphase stage . This inhibition of cell division ultimately results in the death of rapidly dividing cancer cells . Additionally, this compound may interfere with nucleic acid and protein synthesis by blocking the utilization of glutamic acid .

Vincristine belongs to the Vinca alkaloid family, which includes vinblastine, vindesine, vinorelbine, and vinflunine. These compounds share a core structure but differ in substituents, leading to variations in potency, toxicity, and clinical applications.

Mechanistic Differences in Tubulin Binding and Microtubule Dynamics

• This compound vs. Vinblastine : While both inhibit tubulin polymerization, vinblastine exhibits stronger antiproliferative effects in cell cultures. For example, in L-cells, 40 nM vinblastine completely inhibited growth, whereas this compound caused only 25% inhibition . However, this compound has a lower Ki (0.085 µM) for tubulin binding compared to vinblastine (0.178 µM), indicating higher intrinsic activity against microtubule assembly .
• This compound vs. Vinorelbine: Vinorelbine induces tubulin self-association into spiral aggregates but forms fewer large polymers compared to this compound . This may explain its distinct clinical profile in non-small-cell lung cancer (NSCLC) .

Clinical Efficacy and Toxicity Profiles

• Neurotoxicity: this compound’s neurotoxicity is more pronounced than vinblastine’s, which predominantly causes myelosuppression .
• Combination Therapy : this compound’s synergy with methotrexate is schedule-dependent. Administering methotrexate before this compound enhances efficacy, whereas the reverse sequence increases toxicity .

Resistance and Novel Formulations

• P-gp Overexpression : this compound is a substrate for P-glycoprotein (P-gp), a drug efflux pump linked to multidrug resistance. Liposomal this compound circumvents this by maintaining high intracellular drug concentrations .
• Novel Derivatives: Semisynthetic compounds like vinepidine show comparable tubulin inhibition (Ki: 0.079 µM) to this compound but weaker in vivo activity, highlighting the role of non-tubulin targets (e.g., calmodulin) in efficacy .

Comparative Cytotoxicity in Preclinical Models

Table 1. IC50 Values (µM) of Vinca Alkaloids in Human Cancer Cell Lines

• Neuroblastoma : this compound’s potency (IC50: 0.015 µM) is enhanced by pirinixic acid derivatives, which sensitize resistant cells by inhibiting survival pathways .

Basic Research Questions

Q. What experimental models are most effective for studying Vincristine-induced neurotoxicity, and how should variables be controlled?

this compound’s neurotoxic effects are best studied using compartmentalized in vitro models (e.g., microfluidic chambers) to isolate axonal and somatic responses. For example, a concentration of 1 μM this compound applied to axonal compartments induces progressive degeneration, while the same concentration in somatic compartments shows no effect . Key variables to control include exposure duration, drug concentration gradients, and neuronal subtype specificity (e.g., dorsal root ganglion vs. cortical neurons). Include negative controls (e.g., untreated axons) and validate results via morphological (microscopy) and functional (electrophysiology) assays .

Q. What methodologies are recommended for pharmacokinetic analysis of this compound in biological samples?

High-performance liquid chromatography (HPLC) coupled with mass spectrometry (LC-MS/MS) is the gold standard for quantifying this compound in plasma. A vortex-assisted dispersive liquid-liquid microextraction (DLLME) protocol improves recovery rates (≥90%) by optimizing solvent ratios (e.g., chloroform:acetonitrile) and pH conditions (pH 9.0) . Calibration curves should span 0.1–100 ng/mL, with intra-day and inter-day precision maintained at <15% .

Q. How can researchers standardize dosing protocols for this compound in preclinical cancer studies?

Preclinical dosing should align with human equivalent doses (HEDs) calculated via body surface area normalization. For murine models, a typical HED range is 0.5–1 mg/kg administered intravenously weekly. Monitor hematological toxicity (e.g., neutropenia) and neurotoxicity (e.g., gait abnormalities) as endpoints. Use syngeneic or patient-derived xenograft (PDX) models to replicate human pharmacokinetic variability .

Q. What criteria distinguish reliable in vitro efficacy data for this compound across cancer cell lines?

Use cell lines with documented this compound sensitivity (e.g., leukemia Jurkat cells, IC₅₀: 2–5 nM) and resistance (e.g., MCF-7 breast cancer, IC₅₀: >50 nM). Ensure assays include:

• Dose-response curves (6–8 concentrations, 72-hour exposure).
• Proliferation metrics (MTT or ATP-based assays).
• Apoptosis markers (Annexin V/PI flow cytometry). Validate findings with clonogenic assays to assess long-term survival .

Q. How should researchers address batch-to-batch variability in this compound for in vitro studies?

Source this compound from accredited suppliers (e.g., Sigma-Aldrich, Selleckchem) and verify purity (>98%) via certificate of analysis (CoA). Pre-test each batch in a reference cell line (e.g., Jurkat) to confirm IC₅₀ consistency. Normalize data to a positive control (e.g., paclitaxel) to mitigate inter-experimental variability .

Advanced Research Questions

Q. How can high-throughput CRISPR screens identify synergistic drug combinations with this compound?

A CRISPR knockout library (e.g., GeCKO v2) can screen 18 cancer cell lines against 8 drugs, including this compound, to identify gene targets enhancing efficacy. For example, EP300 knockout synergizes with this compound in neuroblastoma models. Use a dual-readout system (cell viability and apoptosis) and validate hits via RNAi or pharmacological inhibition (e.g., JQAD1, an EP300 degrader) . Analyze data with SynergyFinder to quantify combination indices (CI < 0.3 indicates strong synergy) .

Q. What experimental strategies resolve conflicting data on this compound’s efficacy in solid tumors vs. hematological cancers?

Conflicting data often arise from tumor microenvironment (TME) differences. To address this:

• Compare drug penetration using 3D spheroid vs. 2D monolayer cultures.
• Profile ATP-binding cassette (ABC) transporter expression (e.g., P-gp) via qPCR.
• Use intravital imaging to assess this compound distribution in orthotopic models. Apply meta-analysis frameworks (e.g., PRISMA) to harmonize datasets and identify confounding variables .

Q. How can researchers model this compound resistance mechanisms in in vivo systems?

Develop resistance by exposing PDX models to escalating this compound doses over 6–8 weeks. Profile resistance markers via RNA-seq (e.g., upregulated βIII-tubulin, MAPK pathway activation) and validate with CRISPR-Cas9 knockout. Use single-cell sequencing to identify resistant subclones and test combination therapies (e.g., this compound + MAPK inhibitors) .

Q. What advanced imaging techniques optimize this compound delivery studies in the blood-brain barrier (BBB)?

Two-photon microscopy tracks this compound extravasation in real-time using fluorescent analogs (e.g., BODIPY-Vincristine). Combine with dynamic contrast-enhanced MRI to quantify BBB permeability changes in glioblastoma models. Validate delivery efficiency via LC-MS/MS of brain homogenates .

Q. How should multi-omics datasets be analyzed to uncover this compound’s off-target effects?

Integrate transcriptomic (RNA-seq), proteomic (TMT labeling), and metabolomic (LC-MS) data using platforms like MetaboAnalyst or IPA. Focus on pathways enriched in neurotoxicity (e.g., axon guidance, microtubule dynamics) and validate candidates (e.g., MAP1B, CRMP2) via siRNA knockdown. Use machine learning (e.g., random forest) to prioritize biomarkers .