Al-Walid A. Mohsen, Ph.D.

  • Research Associate Professor of Pediatrics

Al-Walid A. Mohsen has a dual role. His primary role has long been to provide Vockley’s research personnel with experimental design support and research direction to pursue the specific aims of his NIH grants and his biotech-funded projects. Mohsen has for years been a driver of discovery and innovation. His protein structure insight led him to identify the N-terminus amino acid sequence of ACAD8 hypothetical protein and its identity as isobutyryl-CoA dehydrogenase. He has also identified a structural “twin” for potato isovaleryl-CoA dehydrogenase (IVD) being 2-methylbutyryl-CoA dehydrogenase rather than an IVD isoenzyme. In the last three years, he pioneered a novel concept with breakthrough potential in drug discovery for treating biochemical genetic disorders with his current focus being therapies for fatty acids oxidation disorders. With his novel biochemical concept, he demonstrated how inhibiting the last downstream enzyme reaction in biochemical pathways can induce pathway intermediates’ chaperone effect as the intermediates are either not released or bind back to their respective enzymes and contribute to stabilizing the pathway enzymes. Not only the intermediate(s) of a specific unstable mutant enzyme stabilizes the enzyme, but by stabilizing other enzymes in the pathway/complex secondary stabilization through protein-protein interaction is possible. Another area where he leads innovation is “Designer Triglycerides” where he is building on the limited success of triheptanoin, a.k.a., triheptanoylglycerol, in treating VLCAD and taking it to the next level as a tool to deliver biochemical intermediates that are in shortage. Designer Triglycerides consist of various glycerol-linked compounds or oils having selected biochemical intermediates that are meant to bypass the metabolic blocks in fatty acid oxidation disorders or others. Confirming the mechanisms and the pharmacodynamics and characterization of the proposed drug therapies for five fatty acid mitochondrial metabolic disorders, on the molecular level in vitro and in vivo, will help in submitting an NDA to the FDA.

In addition to his own research interests, Dr. Mohsen is overseeing projects to evaluate the efficacy of new therapies using in vitro and in vivo models for more than five Pharmaceutical companies.

Major Lectureships and Seminars

  • Pediatric Innovation Retreat, PittMcGowan, University of Pittsburgh, Pittsburgh, PA.   
    • Oral presentation title: Inhibiting Distal Biochemical Pathway Reactions: A Novel Therapeutic Chaperone Strategy for Inherited Metabolic Disorders, July 13, 2018
  • The International Network for Fatty Acid Oxidation Research & Management (INFORM), Athens, Greece. 
    • Oral presentation title: 
      Structural Insights into Drug Therapy of FAODs, Sept 2, 2018
  • Society for the Study of Inborn Errors of Metabolism (SSIEM), Athens, Greece
    • Oral presentation title:  
      Structural Insights into drug therapy of fatty acid oxidation disorders, Sept 4, 2018

Professional Affiliations/Society Memberships

  • Society of Inborn Errors of Metabolism, USA
  • Society for the Study of Inborn Errors of Metabolism, European Union

Education & Training

  • B.S.: Biochemistry, Ain-Shams University 1982, Cairo, Egypt
  • M.S.: Nutrition, University of Auburn 1988, AL, USA
  • Ph.D.: Enzymology and Protein Structure/Function, University of Auburn 1992, AL, USA
  • Fellowship: Mayo Clinic, Rochester, MN, USA

Representative Publications

View Dr. Mohsen's full list of publications from PubMed.

Pitt Innovation Institute Collaboration

With several innovative therapies under development, Dr. Mohsen is working closely with the Innovation Institute at the University of Pittsburgh seeking funding for a Biotech startup that would focus on finding therapies for fatty acids oxidation and energy metabolism disorders. Visit this Innovation Institute EnergXT link to find out more.

Patents Contribution

Patents Issued

  • Treatment of medium-chain acyl-CoA dehydrogenase deficiency, Pitt# 02591; PCT/US2013/036739, Patent# US 9,283,200, filing date Feb 25, 2015; Published WO/2013/158616, Oct 24, 2013.

Patents Under Review

  • Methods of treatment of rhabdomyolysis, Pitt# 03744, PCT/US2016/058071, filing date: Oct 21, 2016; Published WO/2017/070445, April 27, 2017.
  • Anaplerotic Agents for Treatment of Disorders of Propionate and Long Chain Fat Metabolism, Pitt# 03786; PCT/US2017/028100, filing date April 04, 2017 (under renewal); Published WO/2017/184583, Oct 26, 2017.
  • Electron, Radical, or Reactive Oxygen Species-Scavenging Agent Based Therapy of Inborn Errors of Fatty Acid Oxidation and Oxidative Phosphorylation, Pitt# 03927; PCT/US2017/031312, filing date May 5, 2017; Published WO/2017/193000, Sept 11, 2017
  • Development of acyl-CoA dehydrogenases micro/nano enzyme assay for clinical diagnosis and newborn screening, Pitt# 03664; US 2018/00231130, filing date July 21, 2017; Published Jan 25, 2018.
  • Therapy for mitochondrial fatty acids b-oxidation disorders, Pitt# 03999; PCT/US2017/061712, filing date Nov 15, 2017; Published WO2018/093839, May 24, 2018.

Research Interests

Development of Chemical Chaperone for Inherited Metabolic Enzyme Deficiencies. Genetic disorders resulting from missense mutations can often render the mutated proteins structurally defective, leading to their misfolding or instability. Mutant enzymes that assume a native tertiary or quaternary assembled state may have partial activity. Being a component of a complex or supercomplex may also induce secondary biochemical dysfunctions. Such mutant enzymes are usually thermolabile and vulnerable to proteolysis, making fever, strenuous exercise, or other stress factors life-threatening decompensation triggers, if the accumulated metabolites are toxic or a decrease in the level of the metabolite is lethal. Often protein thermostability and vulnerability to proteolysis improve significantly by ligand binding. Ligands that improve protein stability include the protein/enzyme’s own substrate, a substrate analog, or its reaction product(s). Other stabilizing ligands also include ones that bind to allosteric sites or small chaperone molecules that provide stability through other molecular mechanisms. Although screening for small chaperone molecules that bind enzymes at sites away from their catalytic sites to stabilize structurally compromised mutants has been a major rationale for drug development, stabilizing molecule(s) such as the enzyme’s own reaction product or pathway intermediates of the distal pathway steps may provide such stabilizing effect. Inhibitors of downstream pathway reactions may increase the presence of a defective but partially functional enzyme’s product or other pathway intermediates in situ to levels high enough to bind back to the defective enzyme/protein. This is the basis for the concept that Mohsen introduced, which has the potential to be a breakthrough in drug discovery for genetic disorders. The validity of his concept, now named inhibitor-induced in situ chaperone therapy (I3CT), was tested in three different biochemical pathways where patient cells with missense mutations were treated with three known drugs that are inhibitors of distal reactions: fatty acid b-oxidation, leucine metabolism, and phenylalanine metabolism pathways.

Development of an I3CT for Fatty Acid β-Oxidation Cycle Enzyme Deficiencies. Mitochondrial fatty acid b-oxidation cycle is a spiral pathway that includes four enzymatic reaction steps. Inherited defects in the ACADVL or HADHA/HADHB genes coding for the VLCAD and TFP proteins, respectively, are the cause of some of the most serious life-threatening metabolic disorders. Although VLCAD deficiency is the most common among the long-chain fatty acids defects, TFP deficiency shows more life-threatening symptoms. VLCAD deficiency results in a decrease in energy output from long-chain fatty acid b-oxidation, causing the heart, which draws ~80% of its energy requirement from long-chain fatty acids, to be at risk of cardiomyopathy. More than 65 of the mutations identified in patients with defects in the ACADVL gene are missense mutations, which are hypothesized to cause instability. Trimetazidine (TMZ), is an inhibitor of long-chain ketoacylthiolase (LCKAT) recognized to slow long-chain fatty acid b-oxidation enough, shifting cardiac energy fulfillment from fatty acid oxidation to glucose oxidation, and it is used to treat angina pectoris induced by ischemia of the heart. Compared to conventional therapy, TMZ is reported to have shown significant improvements in non-ischemic and ischemic cardiomyopathy. Because it is an inhibitor of LKCAT, Mohsen examined the effect of TMZ on the presence of b-oxidation enzymes in patients with b-oxidation disorders. Experimental results supported the concept, showing a positive effect of TMZ FAO disorders patient cells. In combination with PPARd agonists that increase transcription of FAO proteins, TMZ showed synergistic efficacy as the increase in markers doubled in VLCAD patient cells supporting the hypothetical mechanism of action and providing best hope for patients for effective therapy in many patients with FAO disorders including CPT II, MCAD, VLCAD, LCAHD, and TFP deficiencies.

Development of Chemical Chaperone for MCAD Deficiency. Deficiency of MCAD rivals PKU as the most common biochemical genetic disorder. Patients with MCAD deficiency are asymptomatic at birth but are at risk for episodes of acute, life-threatening hypoglycemia. They usually first occur between three and 24 months of age but can occur at any age in association with physiologic stress, such as fasting or infection. The mortality rate during an acute crisis in previously undiagnosed patients pushes 20%. Newborn screening via tandem mass spectrometry now identifies MCAD deficiency pre-symptomatically, nearly eliminating mortality from the disease. However, treatment requires lifelong dietary monitoring, and significant morbidity still occurs due to hospitalizations for intravenous glucose therapy in the face of reduced oral intake. A single mutation in the MCAD gene (a G985A point mutation) has been identified in 90% of the alleles in the MCAD gene in deficient patients. The K304E destabilizes the quaternary structure of the enzyme, and the resultant mutant protein is rapidly degraded. In vivo, the mutant protein is catalytically active when stabilized, a restoration on of only a few percent of normal MCAD activity will restore near-normal metabolic balance in patients. The objective of this current research is to establish the drugability of the MCAD K304E mutant by identifying lead compounds that can stabilize the mutant protein using in vitro and in silico approaches. Mohsen’s current research has led to three different drug-development approaches.

  1. Targeting the substrate binding site by using substrate analogs as stabilizing agents. An example that has seen success is the use of phenylbutyrate to stabilize the protein in vivo and provide thermal stability. Mohsen’s studies led to a clinical trial led by Horizon Pharma to evaluate the effects of the drugs Buphenyl (sodium phenylbutyrate) and Ravicti (glycerol phenylbutyrate) on patients with MCAD K304E and their biochemical acylcarnitine profiles. Mohsen will continue with detailed characterization of various glycerol phenylbutyrate formulations on other MCAD-deficient cell lines harboring other missense mutations and use a mouse model with the MCAD K304E mutation to better understand the pharmacokinetics.
  2. Targeting remote pharmacophore sites to identify ligands that can bind to known sites on the MCAD tetramer and that have stabilizing pharmacophore characteristics. Using molecular modeling, Mohsen has identified the electron transfer flavoprotein docking site as a drug-development target for MCAD and other ACADs. A mutant 12-mer peptide designed to bind to the docking site increased thermal stability by 2–2.5°C. The proof-of-concept finding was critical in pursuing this site for drug design. Future experiments will focus on this peptide, and its structure will be used to scaffold fragment-based drug design and in silico screening.
  3. Development of an I3CT to treat MCAD deficiency. Patients’ fibroblasts with MCAD K304E mutation respond positively to TMZ treatment. The increase in enzyme activity and protein presence is hypothesized to be due to inhibition of the medium-chain 3-ketoacyl-CoA thiolase in a mechanism similar to the case of the long-chain acyl-CoA mentioned above.
  4. Use of chaperone generating agents, namely glycerol phenylbutyrate formulations or trimetazidine in combination with PPARd agonist, which was shown to increase VLCAD mutant presence. Mohsen found that the combination of trimetazidine and a PPARd agonist tripled the effect of either alone.

Optimization of Anaplerotic Agents for Treating β-Oxidation Disorders. Triheptanoin (commercially known as UX007) is a synthetic C7 fatty acid triglyceride that in clinical trials to treat long-chain fatty acid oxidation disorders and glucose transporter 1 deficiency. Although clinical trials using UX007 have shown positive indicators and met some endpoints (unpublished), they have not alleviated the rhabdomyolysis and missed endpoints in phase II for the latter indication. Mohsen has proposed to compare the use of other branched chain organic acids to compare their efficacy in alleviating the biochemical phenotypes of many of the energy pathway deficiencies. Mohsen will continue to refine some of the anaplerotic agents and look for metabolic phenotype differences.

Development of Chaperone for Leucine Metabolism Pathway Disorders. Using the I3CT concept, Mohsen identified a potential drug therapy for patients afflicted with Leucine metabolism pathway disorders. Treating patient cells with various Leucine metabolism pathway disorders with epigallocatechin gallate (EGCG), a naturally occurring co- pound found in green tea, is promising. The intent is to use EGCG, the enzyme that catalyzes the end-product step of the leucine catabolism pathway, to slow pathway intermediates’ generation and accumulate ones that can bind back to enzymes and catalyze reactions in the pathway. Several diseases can be targeted with this treatment. Follow-up experiments will be carried out to prepare for clinical trials.

Elucidating the Function of New ACADs and Detailing the Roles of ACAD10 and ACAD10 in Physiology. Identification of roles for ACAD10 and mouse Acad12 in physiology. ACAD10 has been implicated in diabetes in humans. Acad10 knockout mice experiments have confirmed a relationship. Although ACAD10 protein has an ACAD domain that is very similar to the ACAD family of enzymes, it also has an extra-large domain that Mohsen hypothesizes is an electron transfer domain that likely binds NAD. Moreover, its active site according to the crystal structure of ACAD11 and modeling seem to contain basic residues, implying possibly more than just an α,β-dehydrogenation biochemical function, but perhaps another function comparable to glutaryl-CoA dehydrogenase, which has an additional decarboxylation function. Another exciting result from the investigations of ACAD10 in mice is the confirmation of the presence of another ACAD protein, ACAD12. This one is surprisingly very similar to a short peptide at the N-terminus, ~160 amino acids, plus the ACAD domain of ACAD10 to almost 97% homology. Mohsen is currently pursuing the identification of the function of this version of an ACAD.

Differentiation of Roles for ACAD9 and VLCAD Variant 3 in Physiology. A mitochondrial β-oxidation spiral is mostly known to start with VLCAD for long-chain substrates. Whereas ACAD9 seems to utilize mostly unsaturated fatty acids and has been implicated to have a role as an assembly factor interacting with ECSIT, an apparent VLCAD variant, named variant 3, has never been studied for function and role in physiology; only its isoenzyme VLCAD short has been studied. The latter is more specific to very long (>16 carbon chain length), saturated acyl-CoAs, respectively. Recombinant ACAD9 has activity toward saturated and unsaturated long-chain acyl-CoA substrates, but it is not upregulated in the case of VLCAD deficiency. Mohsen is studying this mechanism.

Characterization and Stability Studies of Isovaleryl-CoA Dehydrogenase (IVD) Naturally Occurring, Disease-Causing Missense Mutations. Lately, many naturally occurring missense mutations found in IVA patients have been introduced into recombinant IVD cloned in a prokaryotic expression vector. Four were stable enough to produce, and two failed to produce protein in the cell-free extract. Three of the four had activity. Mohsen intends to characterize the mutants and their thermal stability, then assess them as potential targets for therapy.

Division