{"ranked_hypotheses":[{"title":"NAD+ Augmentation and Mitochondrial Quality Control for AD Prevention","description":"Upstream bioenergetic failure (mitophagy impairment, NAD+ depletion) represents the earliest detectable pathology in vulnerable neurons, preceding clinical symptoms by decades. NAD+ boosters (nicotinamide riboside, NMN) have established oral bioavailability and BBB penetration, with the most translation-ready profile. This approach positions neuroprotection as preventive or combinatorial strategy rather than standalone disease modification. SIRT1/3 activation and autophagy modulation offer additional mechanisms but with lower feasibility. The strategy addresses upstream pathology that amyloid clearance cannot reverse.","target_gene":"NAD+ biosynthetic enzymes (NMNATs), SIRT1, SIRT3","composite_score":0.72,"evidence_for":[{"claim":"Mitophagy failure is among earliest detectable changes in AD vulnerable neurons","pmid":"PMC5836949"},{"claim":"NAD+ depletion impairs SIRT1/3-mediated mitochondrial quality control","pmid":"PMC6285032"},{"claim":"NAD+ boosters show neuroprotective effects in AD models","pmid":"PMC6822656"}],"evidence_against":[{"claim":"NAD+ augmentation alone may be insufficient once neurodegeneration is established","pmid":"PMC7219219"},{"claim":"SIRT1 activator resveratrol failed clinically","pmid":"NCT01238161"}]},{"title":"Microglial Reprogramming via TREM2 and PLCG2 Modulation","description":"AD GWAS has identified microglial-expressed risk genes (TREM2, PLCG2, INPP5D) with effect sizes comparable to or exceeding APOEε4. TREM2 agonism and PLCG2 positive allosteric modulation could shift microglia from damaging to protective phenotypes, enhancing Aβ clearance. However, BBB penetration remains the primary barrier, and prior TREM2 agonist AL002 failed Phase II in 2022. Monotherapy is unlikely to match anti-amyloid efficacy; more plausible as combination component. Development cost estimated at $200-400M with 7-10 year timeline to Phase II.","target_gene":"TREM2, PLCG2, INPP5D","composite_score":0.68,"evidence_for":[{"claim":"TREM2 loss-of-function variants impair microglial phagocytosis of Aβ plaques","pmid":"PMC5545969"},{"claim":"PLCG2 P522R variant appears to enhance microglial function","pmid":"PMC5841466"},{"claim":"Microglial genes identified by large-scale AD GWAS with high-effect-size variants","pmid":"PMC5714278"}],"evidence_against":[{"claim":"AL002 (TREM2 agonist) failed Phase II in 2022, demonstrating translation barriers","pmid":"NCT03828747"},{"claim":"Overactivation may dysregulate microglial homeostasis; theoretical cytokine release risk","pmid":"PMC6137679"}]},{"title":"Combinatorial and Preventive Trial Strategies for Network Failure","description":"AD pathogenesis involves networked dysfunction (Aβ → tau → neuroinflammation → synaptic loss → network disruption), yet virtually all Phase III trials test single agents in symptomatic patients. Combination trials (e.g., anti-amyloid + anti-inflammatory) and trials in genetically at-risk asymptomatic individuals remain rare (~5% of pipeline). This represents a strategic gap: network compensation requires multi-target modulation, and intervention in presymptomatic populations offers the strongest biological rationale. However, two-company partnerships, liability allocation, and dosing complexity create significant barriers.","target_gene":"N/A (trial design strategy)","composite_score":0.55,"evidence_for":[{"claim":"Preclinical models demonstrate synergistic effects of combination therapy","pmid":"PMC5841466"},{"claim":"Amyloid clearance alone cannot halt disease progression in symptomatic patients","pmid":"PMC9679791"},{"claim":"Genetically at-risk individuals represent strongest rationale for intervention","pmid":"PMC5714278"}],"evidence_against":[{"claim":"Two-company partnerships are difficult to negotiate","pmid":"N/A"},{"claim":"Liability allocation for adverse events complicates multi-agent trials","pmid":"N/A"}]},{"title":"Anti-Amyloid Monoclonal Antibodies Occupy Disproportionate Trial Space","description":"HYPOTHESIS CONTEXT ONLY - This observation frames the therapeutic landscape but does not constitute an actionable target. Anti-amyloid antibodies (lecanemab, donanemab) demonstrate ~27% CDR-SB slowing, representing genuine efficacy. However, this investment concentration has potentially crowded downstream mechanisms (tau, synaptic dysfunction, network disruption). This framing should inform portfolio strategy but cannot direct target identification.","target_gene":"N/A (pipeline distribution observation)","composite_score":0.30,"evidence_for":[{"claim":"~40% of Phase III trials target amyloid mechanisms","pmid":"AlzForum Pipeline Database 2024"},{"claim":"Aβ oligomers trigger cascading pathology including tau hyperphosphorylation","pmid":"PMC5545969"}],"evidence_against":[{"claim":"Other mechanisms have been tried and failed; correlation does not prove causation","pmid":"N/A"}]}],"synthesis_summary":"The AD clinical trial pipeline exhibits a critical misalignment between genetic evidence and investment allocation. The highest-priority therapeutic hypothesis is NAD+ augmentation targeting upstream mitochondrial/proteostatic mechanisms, which represents the most translation-ready approach given existing safety profiles and oral bioavailability, positioned best for preventive or combinatorial strategies. Microglial reprogramming via TREM2/PLCG2 modulation ranks second, with strong genetic validation but significant BBB penetration barriers following prior TREM2 agonist failure. Combinatorial trial designs and presymptomatic intervention strategies offer conceptual promise but face substantial implementation barriers including multi-company negotiation complexity and regulatory liability concerns. The amyloid-centric investment pattern should be understood as context rather than an actionable target. The fundamental opportunity lies in redirecting resources toward these underfunded but mechanistically validated pathways, particularly as combination approaches addressing the networked nature of AD pathophysiology.","knowledge_edges":[{"source_id":"H3","source_type":"hypothesis","target_id":"NAD+_biosynthetic_enzymes","target_type":"target","relation":"directly_targets"},{"source_id":"H2","source_type":"hypothesis","target_id":"TREM2","target_type":"target","relation":"directly_targets"},{"source_id":"H2","source_type":"hypothesis","target_id":"PLCG2","target_type":"target","relation":"directly_targets"},{"source_id":"H3","source_type":"hypothesis","target_id":"SIRT1","target_type":"target","relation":"directly_targets"},{"source_id":"H3","source_type":"hypothesis","target_id":"SIRT3","target_type":"target","relation":"directly_targets"},{"source_id":"H1","source_type":"hypothesis","target_id":"lecanemab","target_type":"drug","relation":"describes_concentration_of"},{"source_id":"H1","source_type":"hypothesis","target_id":"donanemab","target_type":"drug","relation":"describes_concentration_of"},{"source_id":"H4","source_type":"hypothesis","