Alnylam’s stock slid after it delivered a guidance “one-two punch” by cutting forecasts for its transthyretin amyloidosis franchise amid demand normalization after Amvuttra’s early launch spike. The company lowered the expected revenue range for the TTR drugs, shifting investor focus back to competitive dynamics in TTR cardiomyopathy, where other therapies including Pfizer’s Vyndamax and BridgeBio’s Attruby have raised the bar. Myriad Genetics, also facing pressure, trimmed its 2026 revenue guidance following an 11% year-over-year revenue drop in Q2. The company pointed to declines across categories—Cancer Care Continuum, Prenatal Health, and Mental Health—citing volume pressure and more conservative assumptions tied to reimbursements and average revenue per test. Together, the updates highlight a near-term pressure cycle for commercialization-heavy biotechs: when growth depends on payer behavior and market share positioning, even modest demand normalization or reimbursement shifts can force early guidance resets. Investors now appear watching whether operational initiatives can offset volume softness and competitive intensity.