Slide 1: July 14, 2026
July 14, 2026
Slide 2: Forward-Looking Statements
FORWARD-LOOKING STATEMENTS This presentation contains forward-looking statements that are being made pursuant to the provisions of the Private Securities Litigation Reform Act of 1995 (the PSLRA) with the intention of obtaining the benefits of the “Safe Harbor” provisions of the PSLRA. This presenta
Slide 3: Call Participants
CALL PARTICIPANTS
Slide 4: Opening Remarks
OPENING REMARKS - -@ Priya Singhal, M.D., M.P.H. r Head of Development 4 Biogen
Slide 5: We continue to demonstrate leadership in Alzheimer's disease with a new mechanism – diranersen
WE CONTINUE TO DEMONSTRATE LEADERSHIP IN ALZHEIMER’S DISEASE WITH A NEW MECHANISM – DIRANERSEN Encouraging emerging profile for 60mg Q24W: • CDR-SB effect showed clinical decline by 0.54 points or 26% • Substantial signal on cognition (50% on MMSE, >40% on ADAS-COG 13) • Potential twice yearly admin
Slide 6: Diranersen and the CELIA Study
DIRANERSEN AND THE CELIA STUDY Diana Gallagher Head of Immune Mediated and Neurodegeneration Development 4 Biogen
Slide 7: Diranersen: a differentiated approach in targeting tau
DIRANERSEN: A DIFFERENTIATED APPROACH IN TARGETING TAU Tau is a potentially attractive target in Alzheimer’s disease ¢ AD is a progressive neurodegenerative disease + : . Antibody-based approach characterized by cerebral accumulation of amyloid predominately targets extracellular tau plaques and tau
Slide 8: Phase 2 CELIA study designed for dose response for CDR-SB at 18 months
PHASE 2 CELIA STUDY DESIGNED FOR DOSE RESPONSE FOR CDR-SB AT 18 MONTHS All participants received IT injection (diranersen or Placebo) every 12 weeks to Week 72 * Study designed to detect a signal and Placebo (Q12W) identify a dose ¢ Primary endpoint of a pre-specified ro a) dose response on CDR-SB a
Slide 9: Baseline demographics and characteristics were well balanced
BASELINE DEMOGRAPHICS AND CHARACTERISTICS WERE WELL BALANCED1 AND CONSISTENT WITH OTHER AD TRIALS2,3 Diranersen Low Diranersen Mid Diranersen High Demographic Placebo Q12W 60 mg Q24W 115 mg Q24W 115 mg Q12W (n=115) (n=60) (n=115) (n=116) Age (years), mean (SD) 68.6 (7.4) 67.9 (7.4) 67.3 (7.9) 69.2 (
Slide 10: Diranersen was favored for most endpoints at every dose
DIRANERSEN WAS FAVORED FOR MOST ENDPOINTS AT EVERY DOSE Measure Result Dose Response on CDR-SB € Did not meet primary endpoint assessing dose response Tau-PET © Favors diranersen Tau-CSF @ Favors diranersen CDR-SB © Favors diranersen - including cognitive and functional subdomains ADAS-—Cog 13 @ Fav
Slide 11: CDR-SB effect comparable to anti-amyloid therapies at the 60mg Q24W dose
CDR-SB EFFECT COMPARABLE TO ANTI-AMYLOID THERAPIES AT THE 60mg Q24W DOSE cD Ba a1sen 6 2A 2.9 4|Diranersen 6O mg Q24w n=60 } Diranersen 115 mgQ24w | n=115 Diranersen 115 mg Q12W 25 T T 0 Analysis visit, weeks 24 48 76 Adjusted mean change from baseline (SE) Diranersen 6Omg (low) dose slowed decline
Slide 12: 60mg Q24W demonstrated a promising efficacy profile across multiple endpoints
60mg Q24W DEMONSTRATED A PROMISING EFFICACY PROFILE ACROSS MULTIPLE ENDPOINTS Diranersen with anti-amyloid agents* 26% 42% 50% 0% 23% 30% 60mg Q24W ¢ Robust cognitive effects - markedly higher 42% amyloid treatments Emerge 9, Cy 9 NCT02484547 22% 21% 18% ¥ 42% for ADAS-COG 13 Engage noT0D477800 12%
Slide 13: Slowing of decline observed across cognitive and functional subdomains of CDR in all doses
SLOWING OF DECLINE WAS OBSERVED ACROSS COGNITIVE AND FUNCTIONAL SUBDOMAINS OF CDR IN ALL DOSES Worsening Worsening Adjusted mean change (+SE) Adjusted mean change (+SE) 0 O14 02 03 04 05 Cognitive domains (Week 76) Memory Orientation Judgement and Problem Solving —* Placebo Diranersen } —® Diranerse
Slide 14: Diranersen is the only tau directed agent to show substantial tau reduction in CSF and brain
DIRANERSEN IS THE ONLY TAU DIRECTED AGENT TO SHOW SUBSTANTIAL TAU REDUCTION IN THE CSF AND BRAIN total tau $—___4—__+ 3 > 50-65% reduction from 8-08 A : Bo baseline in soluble total tau cx . § B06 in CSF across dose arms at 52 oa Baseline Week 72 BB | Placebo q12w n=115 . ES go | dimen oomewaw neo *
Slide 15: Diranersen was generally well tolerated
DIRANERSEN WAS GENERALLY WELL TOLERATED Number of participants with variable, n (%) Diranersen 60 mg Q24W (n =61)¢ Diranersen 115 me Q24w (n = 115) Diranersen 115 mg Q12wW (n = 116) Most AEs were mild or moderate in severity, and did not result in study drug withdrawal Any AE 106 (93.0) 60 (98.4) 11
Slide 16: Closing Remarks
CLOSING REMARKS - -@ Priya Singhal, M.D., M.P.H. r Head of Development 4 Biogen
Slide 17: Next steps for the diranersen program
NEXT STEPS FOR THE DIRANERSEN PROGRAM >) An ongoing long-term extension study is continuing to evaluate the long-term safety, tolerability and durability of diranersen in early Alzheimer’s disease ) Ongoing analyses of the data expected to be presented at key upcoming medical congresses and in the l
Slide 18: Phase 2 CELIA data establishes proof of concept and supports moving diranersen to registrational studies
PHASE 2 CELIA DATA ESTABLISHES PROOF OF CONCEPT AND SUPPORTS MOVING DIRANERSEN TO REGISTRATIONAL STUDIES Diranersen: Encouraging emerging clinical profile with unprecedented impact on tau reduction and cognition • With 94% of patients who completed the study continuing to the LTE A well tolerated sa
Slide 19: Biogen
= Biogen.
Slide 20: Appendix
APPENDIX ® Biogen
Slide 21: Unprecedented reductions from baseline in CSF total tau and tau PET SUVR across all dose groups
UNPRECEDENTED REDUCTIONS FROM BASELINE IN CSF TOTAL TAU AND TAU PET SUVR WERE OBSERVED ACROSS ALL DOSE GROUPS 0.2 =® Placebo Diranersen 60 mg Q24W Screening Tau PET substudy: SUVR in whole brain grey matter“ Diranersen 115 mg Q24w lR Diranersen 145 mg Q12W 0.0 Adjusted mean change from baseline (+SE