Scope and sourcing decisions recorded for the next curator. No node asserts that this class lacks the cranial and coronary vasoconstriction the triptans carry, although that is the usual clinical reason for choosing it. Four PubMed searches were run for a citable statement of it -- for gepant cardiovascular safety against the triptan contraindication, for the class reviews of 2023, for the receptor pharmacology, and for the gepants by name against a lack of vasoconstrictive properties -- and the abstracts returned either did not make the claim or made it about the 5-HT-acting drugs in the same sentence. Module snippets are matched against the abstract, so a full text that carries it cannot be quoted here. The claim is left unmade rather than stretched out of an adjacent sentence. The hepatic node is scoped to a first-generation agent on twice-daily dosing, which is what the cited trial tested, and the authors' own conclusion separating the mechanism from the molecule is quoted beside the finding; it is not a class claim about the gepants now in use. The acute and preventive consequences are kept as two nodes rather than one because the trials measure different things, a single attack against monthly migraine days, and collapsing them would imply a comparability the evidence does not support.
Does antagonism of the AMY1 receptor contribute to the clinical effect, or to the adverse effects, of the drugs that block the CGRP receptor?
KNOWLEDGE GAP
cgrp_amy1_off_target_clinical_significance
Attached to:
CGRP Receptor Antagonist Occupancy
This module's trigger asserts that these drugs act by occupying the CGRP receptor, and binds CALCRL and RAMP1 accordingly. The pharmacology review it cites reports that the same antagonists also antagonise the closely related AMY1 receptor, that selectivity parameters cannot be given for all of them because the data are missing, and that the clinical implications are unknown. If AMY1 antagonism contributes, then the trigger as written names only part of what the drugs do, and an adverse effect attributed to CGRP blockade may belong to a different receptor. This is a genuine unknown rather than an uncurated fact: the selectivity measurements have not been made for every agent, and the clinical question has not been asked.
Proposed experiments:
Matched CGRP and AMY1 receptor selectivity panel across the marketed antagonists
CGRP Receptor Antagonist Occupancy
trigger
An antagonist binds the calcitonin gene-related peptide receptor, the heterodimer of calcitonin receptor-like receptor and receptor activity-modifying protein 1, and prevents CGRP from activating it. Two kinds of molecule do this: the small-molecule gepants, and one antibody directed at the receptor rather than at the peptide.
Used by disorders
Migraine
as Gepant Occupancy of the CGRP Receptor
Downstream
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Blockade of CGRP Receptor Signalling
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Hepatic Aminotransferase Elevation on Daily First-Generation Gepant Dosing
Show evidence (3 references)
"These are divided into two major classes, antibodies which bind to the CGRP peptide, preventing it from activating CGRP receptors and receptor antagonists."
Draws the line this module's scope follows: the ligand-binding antibodies are a different class from the receptor antagonists.
"Within the receptor antagonist class, there are two mechanisms of action, small molecule receptor antagonists and an antibody antagonist."
Establishes that both molecule kinds modelled on this node are receptor antagonists, which is why they share one trigger.
"We tested erenumab, a fully human monoclonal antibody that inhibits the calcitonin gene-related peptide receptor, for the prevention of episodic migraine."
Confirms that the antibody in this module acts on the receptor rather than on the peptide, which is what admits it here.
Blockade of CGRP Receptor Signalling
central effector
Occupancy translates into loss of signalling through the receptor, and so into loss of the CGRP-dependent vasodilator and nociceptive responses that sustain an attack. This is the step both the acute and the preventive endpoint run through, and it is the key conformance target.
Downstream
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Acute Termination of a Migraine Attack
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Reduction in Monthly Migraine Days on Receptor-Directed Prevention
Show evidence (2 references)
"It also touches upon the recent development of antagonists and antibodies at calcitonin gene-related peptide (CGRP) and its receptors, which produce a direct blockade of the CGRPergic vasodilator mechanisms involved in migraine."
States that these drugs block the CGRP-dependent vasodilator mechanism of migraine, which is this node.
"CONCLUSIONS: These data suggest a potential role for CGRP receptor antagonism in migraine prophylaxis."
Attributes a therapeutic role to receptor antagonism as a mechanism rather than to any one agent, which is the level this node sits at.
Acute Termination of a Migraine Attack
consequence
Taken during an attack, a gepant raises the chance of being pain free at two hours and of losing the symptom the patient minds most. The absolute size is modest and the placebo rate is high, so the therapeutic gain over placebo is of the order of seven to eleven percentage points; both the treated rate and the placebo rate belong on this node, because the treated rate alone would overstate the class.
Show evidence (2 references)
"Pain freedom at 2 hours was reported by 101 of 464 participants (21.8%) in the ubrogepant 50-mg group, 90 of 435 (20.7%) in the ubrogepant 25-mg group, and 65 of 456 (14.3%) in the placebo group"
The co-primary pain endpoint with its placebo comparator, from the phase 3 single-attack trial.
"Absence of the most bothersome associated symptom at 2 hours was reported by 180 of 463 participants (38.9%) in the ubrogepant 50-mg group, 148 of 434 (34.1%) in the ubrogepant 25-mg group, and 125 of 456 (27.4%) in the placebo group"
The second co-primary endpoint, which is the non-pain half of what an acute treatment is asked to do.
Reduction in Monthly Migraine Days on Receptor-Directed Prevention
consequence
Given continuously rather than during an attack, receptor blockade reduces how many days a month a patient has migraine. The effect is real and partial: against a baseline of about eight migraine days, the antibody removed three to four and placebo removed nearly two. The first-generation small molecule reduced monthly headache days by a similar margin before its trial was stopped, which is a broader endpoint than the migraine days this node is named for, since every migraine day is a headache day but not the converse. The two figures are therefore not interchangeable, and what their agreement supports is only that the preventive effect belongs to the mechanism rather than to one molecule.
Show evidence (2 references)
"The mean number of migraine days per month at baseline was 8.3 in the overall population; by months 4 through 6, the number of days was reduced by 3.2 in the 70-mg erenumab group and by 3.7 in the 140-mg erenumab group, as compared with 1.8 days in the placebo group"
The preventive endpoint with its baseline and its placebo comparator, from the receptor-directed antibody trial.
"there was evidence that telcagepant resulted in a larger reduction from baseline than placebo for mean monthly headache days (month 1: 140 mg = -2.9, 280 mg = -3.1, placebo = -1.7; p < 0.05)"
A second, structurally unrelated receptor antagonist reaching a similar preventive effect, which is what supports reading the effect as mechanism-level; graded INDIRECT because the trial was stopped early and the planned analysis was never run.
Hepatic Aminotransferase Elevation on Daily First-Generation Gepant Dosing
adverse effect
A first-generation gepant given twice daily for prevention produced aminotransferase elevations that stopped its trial: all the affected patients were on drug, and two had symptomatic rises that resolved on withdrawal. The finding is recorded against that molecule and that schedule, which is what was tested, and the trial's own conclusion separated the liability from the mechanism. It is not a class claim about the agents now in use.
Show evidence (3 references)
"RESULTS: The trial was terminated following a recommendation from the Safety Monitoring Board due to hepatotoxicity concerns."
The outcome that makes this a node rather than a footnote: the liability was serious enough to stop the trial.
"Thirteen patients, all in the telcagepant groups, had an alanine aminotransferase (ALT) elevation ≥ 3 × the upper limit of normal"
Quantifies the signal and records that every affected patient was on drug rather than placebo.
"However, the observed aminotransferase elevations do not support the use of telcagepant for daily administration."
The authors' own scoping of the finding to the molecule and its schedule, which is why this node does not generalise it to the class.
Oral Gepant Therapy for Acute Migraine
Platform:
Small molecule
Ubrogepant and rimegepant, taken during an attack as a migraine-specific acute treatment that acts on the CGRP receptor rather than on a serotonin receptor.
Evidence: 2
Oral Gepant Therapy for Migraine Prevention
Platform:
Small molecule
Atogepant, a small molecule taken daily to reduce attack frequency rather than to treat an attack. It engages the same receptor as the acute gepants, on a continuous schedule.
Evidence: 2
Receptor-Directed Antibody Therapy for Migraine Prevention
Platform:
Monoclonal antibody
Erenumab, given monthly by subcutaneous injection. It is an antibody rather than a small molecule, and it is directed at the CGRP receptor rather than at the peptide, which is what admits it to this module where the peptide-directed antibodies are out of scope. It is kept as its own treatment rather than listed beside atogepant because therapeutic_modality is single-valued and the two agents are different platforms, so one tag cannot be true of both.
Evidence: 2