Insmed Incorporated (INSM): Is Brinsupri a >$10B drug? Long-term upside intrigues amid short-term volatility

BofA Securities reiterates its Buy rating on Insmed (INSM.US). The report argues Brinsupri (brensocatib) could represent a >$10B opportunity: KOLs see a credible path for the addressable US population to expand from ~250K today to >500K within 3-5 years and ~1.4M longer term. It breaks the opportunity into four expansion buckets—diagnosed NCFB patients progressing to a 2nd PE (~250K), undiagnosed NCFB (~2.4M), and comorbid COPD (~20M) and asthma (~12M)—with the highest conviction in diagnosed progressors. Including these assumptions would illustratively raise US 2035e sales from $6.2B to ~$15B, though they are excluded from the base case given timing uncertainty. Despite shares being down 42% YTD (vs. NBI +23%), BofA views the selloff—partly an overreaction to the CFO's departure—as undervaluing the launch and offering an attractive entry point. After trimming 2026 EPS to $(2.39) from $(2.32), it lowers the PO to $207 from $214 while reiterating Buy.