Why Is Complement-Mediated Focused Annexon Stock Trading Higher Today?

On Wednesday, Annexon Inc ANNX reported results from the Phase 1 single ascending dose (SAD) and multiple ascending dose (MAD) healthy volunteer study of ANX1502 that targets the active form of C1s responsible for propagating classical pathway activation in association with C1q. 

ANX1502 achieved target serum levels and demonstrated pharmacokinetic (PK) measures that support advancement into a proof-of-concept clinical study to assess pharmacodynamics (PD) and efficacy in patients with cold agglutinin disease in 2024.

The study evaluated single ascending doses of ANX1502 ranging from 25 mg to 1050 mg and multiple ascending doses of ANX1502 ranging from 200 mg twice daily to 525 mg twice daily. The results show:

• Dose-proportional PK and targeted levels of the active drug were observed across both SAD and MAD cohorts.
• Single doses of 525-1025 mg ANX1502 suppressed C4d serum levels in healthy volunteers with higher than median baseline C4d.
• Across all doses evaluated, ANX1502 was generally well tolerated with mild to moderate treatment-emergent adverse events (TEAEs).

Annexon intends to evaluate ANX1502 in complement-mediated autoimmune diseases.

Separately, Annexon outlined a registrational program for ANX007 in geographic atrophy with FDA alignment on vision preservation as the primary endpoint. The program includes

• The Phase 3 ARCHER II global sham-controlled trial is designed to enroll approximately 400 patients with GA secondary to age-related macular degeneration.
• The Phase 3 ARROW Head-to-Head Trial will enroll approximately 500 patients with GA to evaluate a monthly dose of ANX007 versus Apellis Pharmaceuticals Inc's APLS Syfovre (pegcetacoplan).

The FDA has not required Annexon to study the slowing of lesion growth as measured by fundus autofluorescence, an anatomical endpoint used for the approval of other GA programs.

Concurrently, Annexon priced an underwritten public offering of 25 million shares and pre-funded warrants to purchase 18.4 million shares at $2.88/share and pre-funded warrants at $2.879/share, for gross proceeds of $125 million.

Price Action: ANNX shares are up 26.10% at $3.63 on the last check Thursday.