Vitamin B6 Mediator for FdUMP-TS Complex Stability
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Solution Overview
Problem
Current chemotherapy regimens for advanced breast cancer, combining fluoropyrimidines like 5-fluorouracil (FUra) with folinic acid, achieve limited antitumor efficacy due to insufficient expansion of intracellular folate pools, which limits the stability of the TS-inactivating ternary complex, leading to suboptimal cytotoxic effects.
Innovation Solution
Administering high doses of pyridoxine (PN) alongside FUra and folinic acid to enhance intracellular pyridoxal 5'-phosphate (PLP) levels, thereby increasing serine hydroxymethyltransferase (SHMT) activity and expanding intracellular folate pools, specifically 5,10-methylenetetrahydrofolate (CH2-H4PteGlu) concentrations, to stabilize the FdUMP-TS-CH2-H4PteGlu complex and potentiate cytotoxicity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If high dose folinic acid is administered with 5-fluorouracil, then the stability of the TS-inactivating ternary complex is improved, but the expansion of intracellular folate pools is insufficient, leading to limited antitumor efficacy
Solution Approach 1:
Vitamin B6 (pyridoxine) acts as an intermediary substance that enables the conversion of folinic acid to active folate forms through SHMT enzyme activation. By introducing this mediator, the system overcomes the bottleneck of insufficient intracellular folate pool expansion while maintaining ternary complex stability, thereby achieving enhanced antitumor efficacy without directly increasing folinic acid dosage.
Solution Approach 2:
The invention changes the biochemical parameters within the cell by introducing vitamin B6, which alters the intracellular concentration of pyridoxal 5'-phosphate (PLP). This parameter change activates SHMT enzyme, thereby changing the metabolic pathway efficiency and enabling greater conversion of folinic acid to CH2-H4PteGlu, ultimately increasing the folate pool available for ternary complex formation.
2Stability of the object's composition
If higher doses of folate are used to enhance the anticancer effect, then the ternary complex stability increases, but the approach reaches a limit and cannot overcome the plateau in antitumor efficacy
Solution Approach 1:
Vitamin B6 serves as a catalytic intermediary that enhances the efficiency of folate activation through SHMT. Instead of simply increasing folate dosage, this intermediary enables more effective utilization of administered folinic acid, allowing the system to achieve higher ternary complex stability and antitumor efficacy without being constrained by the plateau effect of direct folate dosing.
Solution Approach 2:
The invention introduces a new parameter (vitamin B6 concentration/PLP levels) that fundamentally changes the metabolic rate of folate activation. This parameter change shifts the system from a dosage-limited regime to an efficiency-enhanced regime, where the same or lower folate doses produce greater biological effect through improved enzymatic conversion.
3Productivity
If pyridoxine is administered to expand intracellular folate pools, then the antitumor potency is enhanced, but the mechanism requires understanding of complex enzymatic pathways involving SHMT and PLP
Solution Approach 1:
Vitamin B6 (pyridoxine) is introduced as a simple, well-understood intermediary substance that targets a specific enzyme (SHMT) in the folate metabolic pathway. This approach simplifies the overall mechanism by focusing on a single rate-limiting step (SHMT-mediated conversion) rather than attempting to manipulate multiple complex pathways simultaneously, making the enhanced antitumor potency achievable through a targeted, mechanism-based intervention.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly enhances the antitumor potency of FUra and folinic acid regimens, leading to high response rates with substantial tumor reduction and prolonged progression-free survival in patients with advanced breast carcinoma, without increasing toxicity.
Implementation Method 1
pyridoxal 5'-phosphate (PLP)-dependent enzyme that is the major source of one-carbon units for cellular metabolism
Implementation Method 2
low affinity for binding of SHMT apoenzyme to cofactor. SHMT from various mammalian sources including man was found to bind to cofactor with Kd from 250 nM to as high as 27 μM
Implementation Method 3
binds to thymidylate synthase (TS) and the folate cofactor N5-N10 methylene tetra hydro pteroylglutamate (CH2—H4PteGlu) to form a TS-inactivating [FdUMP-TS-CH2—H4PteGlu] ternary complex
Implementation Method 4
FdUMP-mediated TS inhibition prevents synthesis of thymidine triphosphate (dTTP) leading to deoxy nucleotide triphosphate (dNTP) pool imbalance
Implementation Method 5
results in accumulation of deoxy uridine triphosphate (dUTP) and fluorodeoxyuridine triphosphate (FdUTP), which lead to genomic DNA replication defects including DNA mismatch and altered replication fork progression eliciting DNA damage cell responses and, ultimately, cell death
Data Source
AI summary
An antitumor pharmaceutical composition including (i) a fluoropyrimidine, (ii) a B6 vitamer, and (iii) a folate for its use in the treatment of cancer in a subject in need thereof. The antitumor pharmaceutical composition may be for a simultaneous, separate, or sequential use for the treatment of cancer, and may be administered sequentially or concomitantly with one or more immunotherapeutic, chemotherapeutic or radiotherapeutic agent.