Prothena Corp PLC PRTA
Short PRTA: publicly-available NEOD001 data does not show efficacy — organ responses are likely driven by prior PCD chemo, not the drug, and $1.5B peak sales are unrealistic.
Thesis
Muddy Waters is short Prothena (PRTA), arguing that publicly-available Phase 1/2 data for NEOD001 — its lead AL amyloidosis candidate — does not support efficacy. Patients' biomarker and organ-response improvements are quite possibly attributable to prior plasma-cell directed (PCD) chemotherapy, not NEOD001: Kaufman et al data show organ responses can emerge up to 40 months after hematologic responses, and the uncontrolled 69-patient trial lacked any washout period. The 'Best Response Analysis' is misleading because it isolates peak biomarker improvements and excludes patients with progressive renal dysfunction. Street peak-sales estimates above $1.5 billion are unrealistic given ~4,500 new US cases per year and likely payer pushback on $200-300k per-patient pricing. Insiders hold just 0.04% of shares, consistently sell option proceeds, and PRTA raised $155.3M in March 2017 — all suggesting management itself lacks confidence in NEOD001.
SCQA
Prothena (PRTA) trades at a ~$2.1B market cap predicated on NEOD001, its lead candidate for AL amyloidosis, which sell-side analysts expect to generate $1.5B+ in peak annual sales.
The Phase 1/2 trial is uncontrolled and confounded by prior PCD chemotherapy — organ responses can emerge 40+ months after hematologic responses — while the 'Best Response Analysis' cherry-picks peaks and insiders hold just 0.04%.
Muddy Waters urges PRTA to release individual patient-level NT-proBNP trajectories, dose-specific data, and interim Phase 3 results so investors can judge efficacy independent of the biased 'Best Response' framing.
If NEOD001 fails to demonstrate efficacy — or even if approved, fails to reach $1.5B peak sales given a ~4,500-patient US market and payer resistance at $200-300k per patient — PRTA's valuation collapses.
The three reasons
- 1
NEOD001 organ responses likely caused by prior PCD chemotherapy, not the drug
- 2
'Best Response Analysis' is misleading: cherry-picks peaks, excludes renal-decline patients
- 3
Insiders hold 0.04%, dump option proceeds, and PRTA raised $155M in March 2017
Primary demands
- Release individual patient-level NT-proBNP trial data
- Release dose-specific data for doses between 8.0 mg/kg and the Phase 3 dose of 24 mg/kg
- Release interim data from the Phase 3 trial
KPIs cited
Pattern membership
Where this document fits across the library's 12 rhetorical / structural patterns.
Notable slides (4)
Notes
Classic Muddy Waters biotech short: Word-document memo format with pasted screenshots of PRTA's own Liedtke et al ASH 2016 slides, overlaid with MW's red annotation lines to reframe the data. Key rhetorical moves: (1) reinterpreting the company's own Kaufman et al reference curve to argue organ responses lag hematologic responses; (2) a vivid Mark Whiten 'four-homer game' analogy to discredit the Best Response Analysis; (3) quoting CFO Nguyen verbatim refusing to release patient-level data as evidence of defensiveness. No stake disclosed (standard for shorts). No explicit price target — thesis rests on efficacy failure and unrealistic peak sales, not a valuation framework. Tone is analytical rather than adversarial; villain is unnamed (critiques management collectively).