CGRP Monoclonal Antibodies
The CGRP monoclonal antibodies represent the first migraine-specific preventive therapy class. Four agents are approved, targeting either the CGRP ligand or its receptor. They are effective in both episodic and chronic migraine, have favorable tolerability with no hepatotoxicity or CNS side effects, and require no titration — a major advantage over traditional oral preventives.
Bottom Line
- All four agents reduce monthly migraine days by ~2-4 days vs placebo in episodic migraine, ~2-5 days in chronic migraine
- 50% responder rates: 40-50% in episodic migraine, 27-40% in chronic migraine (vs ~20-25% placebo)
- Onset of action: Benefit seen within the first month for all agents; eptinezumab (IV) shows benefit within 1 day
- No hepatotoxicity, no drug interactions, no CNS depression — main side effects are injection site reactions and constipation (erenumab)
- Superior tolerability vs oral preventives: HER-MES showed discontinuation due to AEs was 10.6% for erenumab vs 38.9% for topiramate
- Effective regardless of medication overuse — no need to withdraw overused medications before starting
- Insurance often requires failure of 2+ oral preventives before approval
Mechanism of Action
Calcitonin gene-related peptide (CGRP) is a 37-amino acid neuropeptide released from trigeminal sensory neurons during migraine. It is a potent vasodilator and plays a central role in trigeminovascular activation, neurogenic inflammation, and pain transmission. CGRP levels are elevated during migraine attacks and normalize with effective triptan treatment.
- Anti-CGRP ligand antibodies (fremanezumab, galcanezumab, eptinezumab): Bind circulating CGRP, preventing it from activating its receptor
- Anti-CGRP receptor antibody (erenumab): Blocks the canonical CGRP receptor itself
All four are large molecules (~150 kDa) that do not cross the blood-brain barrier in significant amounts. Their effect is believed to be primarily peripheral — at the trigeminal ganglion, dural vasculature, and perivascular afferents.
Agent Comparison
| Agent | Target | Route | Dose | Frequency | FDA Approval |
|---|---|---|---|---|---|
| Erenumab (Aimovig) | CGRP receptor | SC | 70 mg or 140 mg | Monthly | EM & CM (2018) |
| Fremanezumab (Ajovy) | CGRP ligand | SC | 225 mg monthly or 675 mg quarterly | Monthly or quarterly | EM & CM (2018) |
| Galcanezumab (Emgality) | CGRP ligand | SC | 240 mg loading, then 120 mg | Monthly | EM & CM (2018); episodic cluster (2019) |
| Eptinezumab (Vyepti) | CGRP ligand | IV | 100 mg or 300 mg | Every 3 months | EM & CM (2020) |
Pivotal Trials: Episodic Migraine
Erenumab
STRIVE (Goadsby et al., NEJM 2017): 955 patients with episodic migraine (4-14 migraine days/month), randomized to erenumab 70 mg, 140 mg, or placebo monthly for 6 months.
- Change in monthly migraine days: -3.2 (70 mg) and -3.7 (140 mg) vs -1.8 placebo (p<0.001 for both)
- ≥50% responder rate: 43% (70 mg), 50% (140 mg) vs 27% placebo
ARISE (Dodick et al., Cephalalgia 2018): 577 patients, erenumab 70 mg vs placebo for 3 months.
- Change in monthly migraine days: -2.9 vs -1.8 placebo (p<0.001)
- ≥50% responder rate: 40% vs 30% placebo
Fremanezumab
HALO EM (Dodick et al., JAMA 2018): 875 patients with episodic migraine, randomized to fremanezumab 225 mg monthly, 675 mg quarterly, or placebo for 3 months.
- Change in monthly migraine days: -3.7 (monthly) and -3.4 (quarterly) vs -2.2 placebo (p<0.001 for both)
- ≥50% responder rate: 48% (monthly), 44% (quarterly) vs 28% placebo
Galcanezumab
EVOLVE-1 (Stauffer et al., JAMA Neurol 2018): 858 patients, galcanezumab 120 mg or 240 mg monthly vs placebo for 6 months.
- Change in monthly migraine days: -4.7 (120 mg) and -4.6 (240 mg) vs -2.8 placebo (p<0.001)
- ≥50% responder rate: 62% (120 mg), 61% (240 mg) vs 39% placebo
EVOLVE-2 (Skljarevski et al., Cephalalgia 2018): 915 patients, similar design. Results consistent with EVOLVE-1.
- Change in monthly migraine days: -4.3 (120 mg) and -4.2 (240 mg) vs -2.3 placebo (p<0.001)
Eptinezumab
PROMISE-1 (Ashina et al., Cephalalgia 2020): 888 patients with episodic migraine, eptinezumab 30 mg, 100 mg, 300 mg IV or placebo quarterly for 12 months.
- Change in monthly migraine days (months 1-3): -3.9 (100 mg) and -4.3 (300 mg) vs -3.2 placebo
- Day 1 response: 300 mg showed significant migraine freedom on the day after infusion compared to placebo — fastest onset of any CGRP mAb
- ≥50% responder rate: 50% (100 mg), 56% (300 mg) vs 37% placebo
Pivotal Trials: Chronic Migraine
| Trial | Agent | N | MMD Reduction vs Placebo | ≥50% Responder Rate |
|---|---|---|---|---|
| Phase 2 CM (Tepper 2017) | Erenumab 70/140 mg | 667 | -2.5 days (140 mg) | 40% vs 23% |
| HALO CM | Fremanezumab 225/675 mg | 1130 | -1.8 to -2.5 days | 38-41% vs 18% |
| REGAIN | Galcanezumab 120/240 mg | 1113 | -1.9 to -2.1 days | 27-28% vs 15% |
| PROMISE-2 | Eptinezumab 100/300 mg IV | 1072 | -2.0 to -2.6 days | 58-61% vs 39% |
CGRP mAbs vs Oral Preventives
Two important trials compared CGRP mAbs directly to traditional oral preventives, demonstrating clear advantages in tolerability:
HER-MES: Erenumab vs Topiramate
Phase 4, double-blind, double-dummy trial comparing erenumab (70-140 mg/month) to topiramate (50-100 mg/day) in 776 patients with episodic or chronic migraine over 24 weeks.
- Discontinuation due to AEs: 10.6% (erenumab) vs 38.9% (topiramate) — dramatically better tolerability
- ≥50% responder rate: 55.4% (erenumab) vs 31.2% (topiramate)
- Mean MMD reduction: -5.9 (erenumab) vs -4.0 (topiramate)
- Quality of life metrics (HIT-6, SF-36) all favored erenumab
APPRAISE: Erenumab vs Oral Preventives After Prior Failures
Phase 4, open-label trial comparing erenumab to standard oral preventives (topiramate, amitriptyline, propranolol) in 621 patients with 1-2 prior preventive failures.
- Patients on erenumab were 6 times more likely to achieve ≥50% MMD reduction (56% vs 17%)
- 11 times more likely to complete treatment and achieve efficacy endpoint
- Switch rate: 2.2% (erenumab) vs 34.6% (oral preventives)
- Supports early use of CGRP mAbs in patients who have failed even one oral preventive
Clinical Implication
- HER-MES and APPRAISE support using CGRP mAbs earlier in the treatment algorithm rather than requiring multiple oral preventive failures
- The tolerability advantage is substantial — nearly 4x lower discontinuation rate
- For patients with contraindications or intolerances to oral preventives, CGRP mAbs can be considered first-line
Efficacy in Treatment-Refractory Patients
Subgroup analyses from pivotal trials and dedicated studies confirm efficacy even in difficult-to-treat populations:
- 2-4 prior preventive failures: All CGRP mAbs maintain efficacy. APPRAISE specifically enrolled patients with 1-2 prior failures and showed robust benefit.
- Medication overuse headache: Post-hoc analyses from HALO CM, REGAIN, and PROMISE-2 show CGRP mAbs are effective regardless of MOH status — no need to withdraw overused medications before starting
- Failed onabotulinumtoxinA: Case series and real-world data show ~30-50% of Botox non-responders respond to CGRP mAbs
Medication Overuse Headache: Key Point
- Unlike traditional preventives, CGRP mAbs work even with concurrent medication overuse
- This simplifies management — start the CGRP mAb while counseling on acute medication limits
- Many patients will naturally reduce acute medication use as preventive therapy takes effect
Galcanezumab for Cluster Headache
Galcanezumab is the only CGRP mAb with FDA approval for episodic cluster headache.
GALiC Trial: Randomized, placebo-controlled trial of galcanezumab 300 mg monthly in episodic cluster headache.
- Attack reduction: -8.7 attacks/week (galcanezumab) vs -5.2 (placebo) over weeks 1-3; difference -3.5 attacks (p=0.04)
- ≥50% reduction: 71% (galcanezumab) vs 53% (placebo)
- A companion trial in chronic cluster headache was negative (no difference from placebo)
- Approved dose for cluster headache: 300 mg SC monthly (higher than migraine dose)
Safety and Side Effects
CGRP mAbs have a favorable safety profile across all phase 3 trials and long-term open-label extensions (up to 5 years of data for some agents).
Common Side Effects
- Injection site reactions (SC agents): Pain, erythema, induration — typically mild and self-limited
- Constipation: More common with erenumab (~3-4%); CGRP promotes GI motility, so blocking it can slow transit
- Infusion reactions (eptinezumab): Nasopharyngitis, hypersensitivity — rare but can include anaphylaxis (<1%)
- Hypertension: FDA added label warning for erenumab in 2021 based on post-marketing reports; monitor blood pressure, especially in patients with pre-existing hypertension
Theoretical Concerns
- Cardiovascular safety: CGRP is a vasodilator; blocking it could theoretically worsen ischemia. Patients with recent MI, stroke, or unstable angina were excluded from trials. Post-marketing data has not shown increased cardiovascular events, but caution is advised in high-risk patients.
- Wound healing: CGRP plays a role in tissue repair. No clinical signal, but theoretically relevant after major surgery.
- Raynaud phenomenon: Case reports of new or worsening Raynaud's, particularly with erenumab. Consider discontinuation if significant.
🔴 Pregnancy and CGRP mAbs
- All CGRP mAbs are IgG antibodies that cross the placenta, particularly in the second and third trimesters
- Animal studies showed no teratogenicity but did show reduced fetal/neonatal growth
- Discontinue before planned conception — half-lives are long (27-32 days); allow 5 half-lives (~5 months) for complete washout
- No adequate human data; pregnancy registries are ongoing
Combination with OnabotulinumtoxinA
For refractory chronic migraine, combining CGRP mAbs with onabotulinumtoxinA (Botox) is increasingly common and supported by growing evidence:
- Complementary mechanisms: OnabotulinumtoxinA inhibits CGRP release from nerve terminals; CGRP mAbs block circulating CGRP or its receptor
- Retrospective data: Multiple case series show ~50-60% of patients inadequately controlled on either therapy alone improve with combination
- Safety: No significant safety concerns with combination; both are well-tolerated
- The COURAGE trial: While testing acute ubrogepant with CGRP mAbs, confirmed high satisfaction and tolerability with CGRP-targeting combination approaches
When to Consider Combination Therapy
- Chronic migraine with partial response to onabotulinumtoxinA (some benefit but still >8 migraine days/month)
- Chronic migraine with partial response to CGRP mAb after 3+ months
- Very high-frequency chronic migraine (>20 headache days/month) where maximal therapy is warranted upfront
- Patient preference to maximize preventive effect before considering other options
Practical Prescribing
Choosing an Agent
- Quarterly dosing preferred? Fremanezumab 675 mg Q3 months or eptinezumab 100-300 mg IV Q3 months
- Fastest onset needed? Eptinezumab IV — benefit observed within 24 hours of first infusion
- Patient prefers self-injection at home? Erenumab, fremanezumab, or galcanezumab (all SC autoinjectors)
- Constipation or hypertension concern? Consider ligand-targeting agents (fremanezumab, galcanezumab, eptinezumab) over erenumab
- Also has episodic cluster headache? Galcanezumab is the only CGRP mAb with FDA approval for cluster (GALiC trial)
- Prior oral preventive failure? APPRAISE supports early CGRP mAb use after even 1 failure
When to Assess Response and Switch
- Assess after 3 months of treatment at adequate dose (AHS consensus). Some patients respond within 1 month; others are slow responders.
- If no meaningful improvement at 3 months, switch to a different CGRP mAb before abandoning the class — ~30-40% of non-responders to one agent respond to another
- Consider switching from receptor-targeted (erenumab) to ligand-targeted (or vice versa) as mechanisms differ slightly
- Combination with onabotulinumtoxinA: Consider for refractory chronic migraine if CGRP mAb alone provides only partial benefit
Cost and Access
Navigating Insurance and Access
- Prior authorization: Most insurers require documentation of failure (inadequate efficacy or intolerance) of 2+ oral preventives (typically from different classes)
- Appeals: If denied, document specific contraindications to oral preventives or reference HER-MES/APPRAISE data supporting early use
- Patient assistance programs: All manufacturers offer programs for uninsured/underinsured patients (Aimovig Ally, Ajovy Complete, Emgality Promise, Vyepti Access)
- Specialty pharmacy: Most CGRP mAbs require specialty pharmacy dispensing; assist patients with enrollment
- Out-of-pocket: Without insurance, list prices are ~$600-700/month; with assistance programs, many patients pay $0-5/month
Long-Term Data
- Open-label extension studies up to 5 years show sustained efficacy without tachyphylaxis
- No new safety signals in long-term follow-up
- Antibody development: Anti-drug antibodies develop in a small percentage (1-6%), mostly non-neutralizing. Neutralizing antibodies are rare and their clinical significance is uncertain.
- Discontinuation: AHS suggests reassessing after 6-12 months of good response. Some patients maintain improvement after stopping; others relapse and require re-initiation. There is no rebound worsening.
Trial Comparison Table
| Trial | Year | Agent | Population | Key Outcome |
|---|---|---|---|---|
| STRIVE | 2017 | Erenumab 70/140 mg | Episodic migraine (n=955) | MMD: -3.2 to -3.7 vs -1.8; 50% RR: 43-50% vs 27% |
| ARISE | 2018 | Erenumab 70 mg | Episodic migraine (n=577) | MMD: -2.9 vs -1.8; 50% RR: 40% vs 30% |
| HALO EM | 2018 | Fremanezumab 225/675 mg | Episodic migraine (n=875) | MMD: -3.4 to -3.7 vs -2.2; 50% RR: 44-48% vs 28% |
| HALO CM | 2017 | Fremanezumab 225/675 mg | Chronic migraine (n=1130) | MMD: -4.6 to -4.9 vs -2.5; 50% RR: 38-41% vs 18% |
| EVOLVE-1 | 2018 | Galcanezumab 120/240 mg | Episodic migraine (n=858) | MMD: -4.6 to -4.7 vs -2.8; 50% RR: 61-62% vs 39% |
| EVOLVE-2 | 2018 | Galcanezumab 120/240 mg | Episodic migraine (n=915) | MMD: -4.2 to -4.3 vs -2.3; confirmed EVOLVE-1 findings |
| REGAIN | 2018 | Galcanezumab 120/240 mg | Chronic migraine (n=1113) | MMD: -4.8 vs -2.7; 50% RR: 27-28% vs 15% |
| PROMISE-1 | 2020 | Eptinezumab 100/300 mg IV | Episodic migraine (n=888) | Day 1 effect; MMD: -3.9 to -4.3 vs -3.2 |
| PROMISE-2 | 2020 | Eptinezumab 100/300 mg IV | Chronic migraine (n=1072) | MMD: -7.7 to -8.2 vs -5.6; Day 1 effect |
| HER-MES | 2022 | Erenumab vs topiramate | EM + CM (n=776) | Discontinuation: 10.6% vs 38.9%; 50% RR: 55% vs 31% |
| APPRAISE | 2024 | Erenumab vs oral preventives | EM, 1-2 prior failures (n=621) | 6x more likely to achieve ≥50% reduction |
| GALiC | 2019 | Galcanezumab 300 mg | Episodic cluster (n=106) | -8.7 vs -5.2 attacks/week; 71% vs 53% responders |
References
- Goadsby PJ, et al. A controlled trial of erenumab for episodic migraine (STRIVE). N Engl J Med. 2017;377(22):2123-2132.
- Dodick DW, et al. ARISE: A phase 3 randomized trial of erenumab for episodic migraine (ARISE). Cephalalgia. 2018;38(6):1026-1037.
- Dodick DW, et al. Effect of fremanezumab compared with placebo for prevention of episodic migraine (HALO EM). JAMA. 2018;319(19):1999-2008.
- Silberstein SD, et al. Fremanezumab for the preventive treatment of chronic migraine (HALO CM). N Engl J Med. 2017;377(22):2113-2122.
- Stauffer VL, et al. Evaluation of galcanezumab for the prevention of episodic migraine (EVOLVE-1). JAMA Neurol. 2018;75(9):1080-1088.
- Skljarevski V, et al. Efficacy and safety of galcanezumab for prevention of episodic migraine (EVOLVE-2). Cephalalgia. 2018;38(8):1442-1454.
- Detke HC, et al. Galcanezumab in chronic migraine (REGAIN). Neurology. 2018;91(24):e2211-e2221.
- Ashina M, et al. Eptinezumab in episodic migraine (PROMISE-1). Cephalalgia. 2020;40(3):241-254.
- Lipton RB, et al. Eptinezumab in patients with chronic migraine (PROMISE-2). Neurology. 2020;94(13):e1365-e1377.
- Reuter U, et al. Erenumab versus topiramate for prevention of migraine (HER-MES). Lancet Neurol. 2022;21(4):341-351.
- Lipton RB, et al. Erenumab vs standard of care in migraine prevention (APPRAISE). Neurology. 2024.
- Goadsby PJ, et al. Galcanezumab for episodic cluster headache (GALiC). N Engl J Med. 2019;381(2):132-141.
- American Headache Society. Consensus statement: the AHS position on integrating new migraine treatments into clinical practice. Headache. 2019;59(1):1-18.