A Rare Disease Story Worth Chewing On; Initiate OP

Research evidence excerpt

A Rare Disease Story Worth Chewing On; Initiate OP

May 12, 2026

Investment Thesis PreliminaryDraft-Confidential

We initiate on BNTC with an Outperform rating and PT of $25.

◼ BB-301 targets a rare but severe genetic disease where muscle weakness drives both quality-of-life decline and life-

threatening complications.

– Disease + unmet need: OPMD is characterized by dysphagia (difficulty swallowing), ptosis, and muscle weakness; can

lead to serious life-threatening complications; no approved disease modifying therapies underscores high unmet need.

– Commercial opportunity: ~15K patients across relevant geographies; blockbuster potential, we model $1.2B peak

unadjusted sales (consensus $1.1B).

– Regulatory path: Planned FDA engagement in mid-2026 should clarify pivotal trial design ahead of a 2027e start.

◼ KOLs constructive on BB-301’s mechanism and Ph1b/2a safety & efficacy; expecting broad uptake.

– Mechanism: elegant fit for underlying genetics, silences and replaces mutant PABPN1 gene via local pharyngeal admin

– Cohort 1: all six patients met responder criteria; longest follow-up now 24 mos w/ deepening benefit over time

– Cohort 2 (high dose): first patient showed substantially greater depth of response at 3 months

– Overall, safe (no TRAEs to date) w/ substantial improvement in patients' ability to swallow; benefit across both

patient-reported dysphagia burden and objective videofluoroscopic-based swallowing measures (gold standard).

◼ Where could we be wrong? The clinical dataset remains driven by a small number of patients in a single-arm, open-label

study; durability beyond the earliest long-term readouts is still being established; regulators may require more work than

expected to align on the pivotal design.