CD38 Inhibition + NAD+ Precursor Synergy for Neuroprotection

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Overview

Executive Summary

Target: CD38/CD157 ectoenzymes + NAD+ biosynthesis 1CD38 in neurodegeneration (Cell 2020)2020 · DOI 10.1016/j.cell.2020.05.020Open reference Approach: Combine CD38 inhibitors with NAD+ precursors to achieve greater NAD+ repletion than either approach alone 2CD38 inhibitors for NAD+ boost (Science 2021)2021 · DOI 10.1126/science.abc8889Open reference Therapeutic Area: Alzheimer’s Disease, Parkinson’s Disease, Aging 3NAD+ repletion in Alzheimer's models (Cell 2016)2016 · DOI 10.1016/j.cell.2016.11.013Open reference Score: 77/100

Mechanism of Action

CD38 Biology

CD38 is a transmembrane glycoprotein that functions as an ecto-NADase, hydrolyzing NAD+ to nicotinamide (NAM) and cyclic ADP-ribose (cADPR). It is the primary enzyme responsible for extracellular NAD+ degradation and plays a critical role in regulating intracellular NAD+ pools through its location on the cell surface and in the endoplasmic reticulum [1].

Key CD38 effects:

  • Hydrolyzes intracellular and extracellular NAD+

  • Produces cADPR, a calcium-mobilizing second messenger

  • Regulates mitochondrial function through NAD+ availability

  • Increases with age - major contributor to NAD+ decline [2]

Therapeutic Rationale

In aging and neurodegeneration, CD38 expression increases in multiple tissues including brain [3]:

  • Alzheimer’s: CD38 elevated in microglia and astrocytes; contributes to NAD+ depletion

  • Parkinson’s: CD38 dysregulation affects dopaminergic neuron viability

  • Aging: CD38 activity increases ~2-3x in brain and peripheral tissues by age 60+

CD38 inhibitors (e.g., apigenin, 78c, AZD0305) have shown [4]:

  • NAD+ preservation in preclinical models

  • Enhanced SIRT1 activity

  • Improved mitochondrial function

However, CD38 inhibition alone may be insufficient because:

  • Basal NAD+ biosynthesis remains impaired

  • Other NAD+-consuming enzymes (PARPs, SARM1) still deplete pools

The synergy: CD38 inhibition prevents NAD+ breakdown while precursors (NMN, NR) boost biosynthesis. Combined effect > sum of parts.

Scoring (10-Dimension Rubric)

Dimension Score Rationale
Novelty 8 CD38 inhibition is newer; combination not yet in trials
Mechanistic Rationale 9 Strong validation for CD38 role in NAD+ decline
Root-Cause Coverage 8 Addresses both NAD+ consumption and biosynthesis
Delivery Feasibility 7 Small molecule inhibitors; brain penetration variable
Safety Plausibility 8 CD38 knockout mice are healthy; therapeutic window exists
Combinability 9 Works with SIRT1 activators, autophagy enhancers
Biomarker Availability 8 NAD+ levels, CD38 activity, cADPR measurable
De-risking Path 7 Can use existing CD38 inhibitor scaffolds
Multi-disease Potential 8 AD, PD, aging, metabolic disease
Patient Impact 7 Addresses fundamental metabolic deficit

Total: 77/100

Actionable Next Steps

Lab Experiments

  1. CD38 inhibitor brain penetration screening: Test existing CD38 inhibitors (apigenin, 78c, AZD0305) in in vitro BBB models and in vivo PK/PD in rodents to identify CNS-penetrant leads

  2. NAD+ precursor combination testing: Combine CD38 inhibitors with NAD+ precursors (NMN, NR) in iPSC-derived neurons from AD/PD patients to measure NAD+ levels, SIRT1 activity, and mitochondrial function

  3. Biomarker validation: Establish CD38 activity in CSF and peripheral blood mononuclear cells (PBMCs) as pharmacodynamic markers

Clinical Protocol Design

  1. Enrichment strategy: Select patients with elevated CD38 expression or confirmed NAD+ deficiency in CSF

  2. Dose-finding design: Start with low-dose CD38 inhibitor (apigenin 50mg daily or 78c 10mg daily) combined with NAD+ precursor (NMN 250mg daily)

  3. Combination protocol: Consider adding SIRT1 activator after CD38 inhibitor loading for maximum NAD+ repletion

Company Partnership Opportunities

  1. Calico/Alapagos (AZD0305): Partner for CD38 inhibitor development and CNS indication

  2. ChromaDex (NR): Partner for NAD+ precursor supply and clinical development

  3. Aberla/Cartherics: Partner for CD38 antibody therapeutics with brain penetration

  4. Tesoro/Beacon: Partner for biomarker development

Combination Therapy Opportunities

Synergistic Targets

  1. + SIRT1 Activators: Maximum NAD+ availability for sirtuin activity

  2. + Autophagy Inducers (TFEB): Enhanced autophagy with preserved NAD+

  3. + PARP Inhibitors: Prevent NAD+ consumption from DNA repair

  4. + Exercise Mimetics: AMPK activation complements NAD+ repletion

Development Pathway

Phase 1: Target Validation

  • Confirm CD38 elevation in AD/PD patient brains

  • Test CD38 inhibitor + NAD+ precursor in iPSC neurons

  • Optimize brain-penetrant CD38 inhibitors

Phase 2: Lead Optimization

  • Develop dual-action CD38 inhibitor/NAD+ precursor molecules

  • Assess chronic dosing tolerability

  • Validate biomarker endpoints

Phase 3: Clinical Translation

  • Design Phase 1/2 trial with NAD+ pharmacodynamics

  • Patient stratification by CD38 expression

Implementation Roadmap

Phase 1: Target Validation & Lead Identification (Months 1-12)

  • Budget: .5-4M

  • Activities: CD38 expression profiling in human brain tissue, iPSC neuron assays, compound library screening

  • Academic Centers: Stanford University (Dr. Katrin Andreasson), NIH National Institute on Aging

  • Milestones: Validated CD38-NAD+ axis in AD/PD brain, 10+ lead compounds identified

Phase 2: Preclinical Development (Months 10-24)

  • Budget: -10M

  • Activities: Lead optimization, GLP toxicology, IND-enabling studies

  • Academic Centers: University of California San Diego (Dr. Lawrence Goldstein)

  • Industry Partners: Alnylam (siRNA delivery), Acadia Pharmaceuticals

  • Milestones: Candidate selected, IND package filed

Phase 3: Clinical Development (Months 24-48)

  • Budget: 5-40M

  • Phase 1: First-in-human, dose-escalation (Months 24-30, -8M)

  • Phase 2: Proof-of-concept in AD/PD (Months 30-42, 0-15M)

  • Phase 3: Registration-enabling trial (Months 42-48, 0-17M)

  • Total Clinical: 5-40M

Total Program Cost: 4-54M over 48 months

Decision Gates

  • Month 12 Go/No-Go: CD38 target validation positive → proceed to preclinical

  • Month 24 Go/No-Go: IND-enabling studies successful → proceed to clinical

  • Month 36 Go/No-Go: Phase 2 efficacy signal → proceed to Phase 3

Risks and Mitigation

Risk Mitigation
Limited CNS exposure Focus on 78c-class with demonstrated brain penetration
Insufficient efficacy alone Position as combination therapy backbone
Off-target effects Use selective CD38 over CD157

Key References

  1. CD38 and NAD+ metabolism in aging (Nature 2019)

  2. CD38 in neurodegeneration (Cell 2020)

  3. CD38 inhibitors for NAD+ boost (Science 2021)

  4. NAD+ repletion in Alzheimer’s models (Cell 2016)

Rubric Score

Dimension Score Rationale
Novelty 7/10/10 CD38 inhibition for NAD+ boosting is emerging; early stage for neurodegeneration
Mechanistic Rationale 8/10/10 CD38 is main NADase; inhibition increases NAD+ levels, enhances sirtuin activity and DNA repair
Addresses Root Cause 7/10/10 NAD+ decline is a fundamental aging mechanism; restoration addresses root cause of cellular decline
Delivery Feasibility 6/10/10 Small molecule inhibitors available; brain penetration being optimized
Safety Plausibility 7/10/10 CD38 knockout mice healthy; chronic inhibition appears safe
Combinability 8/10/10 Synergizes with NAD+ precursors, sirtuin activators, mitochondrial therapies
Biomarker Availability 7/10/10 NAD+ levels measurable in blood; NAD+ metabolites as biomarkers
De-risking Path 7/10/10 Multiple CD38 inhibitors in development; established preclinical efficacy
Multi-disease Potential 8/10/10 Broad relevance for aging, metabolic disorders, neurodegeneration
Patient Impact 7/10/10 Could improve cellular health across multiple organ systems
Total 72/100

Diseases

Mechanisms

Proteins

Cell Types

Treatments

See Also

References

  1. CD38 in neurodegeneration (Cell 2020) Bonafede et al. 2020 · DOI 10.1016/j.cell.2020.05.020
  2. CD38 inhibitors for NAD+ boost (Science 2021) Tarrago et al. 2021 · DOI 10.1126/science.abc8889
  3. NAD+ repletion in Alzheimer's models (Cell 2016) Hou et al. 2016 · DOI 10.1016/j.cell.2016.11.013

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