Alnylam’s Q1 TTR Surge Confirms Growth, but Risks Remain Unresolved

What happened

Alnylam’s Q1 2026 TTR franchise grew 150% year-over-year, driven by Amvuttra’s continued front-line share gains in ATTR-CM, and management maintained full-year TTR revenue guidance of $4.4B–$4.7B despite insurance and pricing headwinds. The headline growth confirms strong demand conversion, but the stock’s price already capitalizes a smooth ramp, leaving little room for error. Underlying risks highlighted in the deep-value analysis—including an active U.S. Attorney subpoena on government price reporting and escalating competition from BridgeBio’s Attruby—remain unaddressed in the Q1 report. The company’s execution is being evaluated against a high bar, as even small quarterly misses have historically triggered sharp drawdowns. While the Q1 results are positive, they do not de-risk the asymmetric downside from potential net pricing compression or compliance remediation.

Implication

The Q1 results confirm Amvuttra is gaining share in ATTR-CM, but guidance maintenance offers no upside surprise, and valuation already embeds this growth. The 150% year-over-year growth is flattered by the low base following ATTR-CM approval in March 2025, making comparable quarters tougher. The subpoena on government price reporting and distributor arrangements remains a binary risk that could compress net pricing across the franchise if it escalates. Competition from BridgeBio’s Attruby is gaining traction (6,629 unique prescriptions by end of 2025), pressuring Amvuttra’s new-start share and potentially requiring higher rebates. Given these uncertainties and the current price near $331—just below the base case $360—the prudent stance is to wait for clearer evidence of sustained net pricing stability and competitive positioning before committing additional capital.

Thesis delta

The Q1 results do not change the fundamental thesis: ALNY remains a high-risk growth story with significant execution and regulatory overhangs. The strong revenue growth and maintained guidance are in line with expectations, so the thesis holds at 'WAIT'—no upgrade or downgrade catalyst emerges. The key nuance is that the company is executing on the top line, but the margin for error is thin, and the stock’s sensitivity to quarterly cadence means a beat on revenue alone may not de-risk longer-term concerns.