Modified Porphobilinogen Deaminase Enzymes for AIP Treatment
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Solution Overview
Problem
Current treatments for acute intermittent porphyria (AIP) are inadequate, as they often lead to recurrent hyper-activation of the hepatic heme synthesis pathway, causing neurological and metabolic manifestations, and are associated with significant morbidity and mortality, with liver transplantation being the only cure but limited by donor availability and complications.
Innovation Solution
Development of modified human porphobilinogen deaminase (PBGD) proteins with specific amino acid mutations, either alone or conjugated with carrier polypeptides like ApoA-I, to enhance enzymatic activity and target the liver, thereby reducing porphyrin precursors accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If current treatments (glucose loading and parenteral heme replenishment) are used to reduce ALA and PBG accumulation, then porphyrin precursor levels decrease, but recurrent hyper-activation of hepatic heme synthesis pathway occurs causing neurological and metabolic manifestations
Solution Approach 1:
The patent applies parameter changes by introducing specific amino acid mutations (N340S, I291M, H199Q, H120Y, S344N) into the PBGD enzyme structure. These mutations alter the enzyme's catalytic properties and stability, enabling sustained reduction of porphyrin precursors without causing recurrent hyper-activation of the heme synthesis pathway, thus resolving the contradiction between immediate efficacy and long-term reliability
Solution Approach 2:
The patent creates a modified copy of the native PBGD enzyme with improved properties. The mutated PBGD variants serve as engineered copies that replicate the enzyme's function while eliminating the drawback of recurrent heme synthesis hyper-activation, providing a reliable long-term solution
2Reliability
If prophylactic heme infusion is applied to prevent recurrent attacks, then acute attacks are reduced, but tolerance develops and frequent application causes thromboembolic disease and hepatic siderosis
Solution Approach 1:
The patent extracts the therapeutic benefit of heme pathway modulation while eliminating the harmful effects of repeated heme infusions. By directly administering mutated PBGD enzyme that sustains heme synthesis regulation, the treatment achieves protective effects without the accumulation of heme iron that causes thromboembolic disease and hepatic siderosis
Solution Approach 2:
The mutated PBGD enzyme provides a single-administration or limited-frequency therapy that replaces the need for frequent heme infusions. Each administration delivers a durable effect, making the treatment analogous to a long-lasting intervention that eliminates the need for repeated short-term interventions with cumulative toxicity
3Reliability
If liver transplantation is performed to cure chronic activation of hepatic heme synthesis, then the life-threatening condition is cured, but donor availability is limited and significant morbidity and mortality occur
Solution Approach 1:
The mutated PBGD enzyme restores the patient's own hepatic heme synthesis pathway function. The engineered enzyme corrects the metabolic defect endogenously, eliminating the need for allogeneic liver transplantation and its associated complexities of donor matching, surgical intervention, and immunosuppression
4Productivity
If modified PBGD proteins with amino acid mutations are developed to enhance enzymatic activity, then deaminase activity increases, but protein stability and pharmacokinetic properties must be maintained
Solution Approach 1:
The patent systematically explores multiple amino acid substitutions at specific positions (N340S, I291M, H199Q, H120Y, S344N) to optimize the balance between catalytic activity and protein stability. Each mutation is selected to enhance deaminase activity while maintaining or improving the enzyme's structural stability and pharmacokinetic properties
Solution Approach 2:
The patent creates composite enzyme structures by combining multiple mutations within the PBGD protein framework. These multi-mutant variants synergistically enhance catalytic activity while the overall protein structure maintains stability, achieving a composite optimization of function and stability
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
The modified PBGD proteins demonstrate increased catalytic activity and improved pharmacokinetic properties, effectively reducing urinary excretion of porphyrin precursors, potentially alleviating acute attacks and extending protection against AIP without the need for frequent heme infusions or liver transplantation.
Implementation Method 1
PBGD is the third enzyme of heme synthesis pathway (EC 4.3.1.8; UniProt Accession #P08397) that catalyzes the loss of ammonia from the porphobilinogen monomer (deamination) and its subsequent polymerization to a linear tetrapyrrole
Data Source
AI summary
The present disclosure relates to human porphobilinogen deaminase derived proteins and polynucleotides and methods of using these proteins and polynucleotides.