Efficacy of Erenumab in Chronic Cluster Headache

Inclusion Criteria (screening) * Adults ≥18 and \< 65 years of age * Documented history of chronic cluster headache for ≥12 months prior to screening according to the International Classification of Headache Disorders-3rd Edition (ICHD-3) * Participants are able to distinguish cluster headache attacks from other headaches. * Insufficient efficacy OR tolerability OR contraindications of approved cluster headache prophylactic medications. Insufficient efficacy and tolerability as determined by the patient. * Sufficient acute attack treatment with triptans or oxygen based on the patient´s history * The patient is able to distinguish cluster headache attacks from other headaches (i.e. tension-type headaches). Inclusion Criteria (Baseline) * At least 9 cluster headache attacks as defined by the ICHD-3 in 7 days during the baseline epoch (SPII), confirmed by patient-reported eDiary entries. * Attacks must have occurred on more than 50% of days of the baseline epoch (SPII). * ≥ 90% patient-reported eDiary compliance during the Baseline epoch, compliance is measured as interacting with e-Diary at least once a day. Exclusion Criteria: * Diagnosis or history of other primary headache diseases according to the International Classification of Headache Disorders, 3rd Edition (ICHD-3), excluding episodic tension type headache and migraine as defined in criterion 2. * Headache freedom from the historic diagnosis of migraine has to be at least one year prior to study inclusion. If patients have on average \<=1 migraine attack per month within a year and can distinguish between migraine attacks and cluster attacks, they are allowed to participate. * Unable to differentiate cluster headache attacks from other headaches * Use of a prophylactic cluster headache medication within 5 half-lives prior to the start of the baseline phase * Parallel use of an SPG stimulator, deep brain stimulation or parallel use of a device for the acute/preventive treatment of chronic cluster headache * Administration of botulinum toxin type A or B in the head or neck area, within 4 months of baseline (SP II) * Concurrent use of other therapeutic monoclonal antibodies. * Current use or any prior exposure to any calcitonin-gene-related peptide (CGRP) antibody, any antibody to the CGRP receptor * Use of other investigational drugs within 5 half-lives of enrollment, or until the expected pharmacodynamic effect has returned to baseline, whichever is longer * Evidence of drug, opioid or alcohol abuse or dependence within 12 months prior to screening, based on medical records or patient self-report * History of use of psilocybin (mushrooms), LSD, MDMA or 2- bromo-LSD within 2 months prior to baseline (SPII) * Have a positive urine drug screen (UDS) for any substances of abuse, except cannabis or cannabinoids, prior to randomization. A retest is applicable if, in judgment of the investigator, there is a reasonable explanation for the positive result. A negative result in the retest is obligatory for entering baseline (SPII) * Diagnosis or history of significant active or unstable psychiatric disease, such as bipolar disorder, schizophrenia, personality disorders, or other serious mood or anxiety disorders. Patients with anxiety disorder and/or major depressive disorder are permitted in the study if they are considered by the investigator to be stable and are taking no more than one medication per disorder. Patients must have been on a stable dose within the 3 months prior to the start of the baseline phase * Score "yes" on item 4 or item 5 of the Suicidal Ideation section of the Columbia Suicide Severity Rating Scale (C-SSRS), if this ideation occurred in the past month, or "yes" on any item of the Suicidal Behavior section, except for the "Non-Suicidal Self-Injurious Behavior" (item also included in the Suicidal Behavior section), if this behavior occurred in the past 3 months. Patients who do not meet this criterion, but who are considered by the judgment of the investigator to be at significant risk for suicide, must be excluded * Active chronic pain syndromes (e.g., fibromyalgia or chronic pelvic pain) in which the pain has lost its guiding and warning function and has acquired an independent disease value. * History or current evidence of major psychiatric disorder (such as schizophrenia, bipolar disorder or type B personality disorder that might interfere with the ability to properly report clinical outcomes) * History or current severe coronary artery disease, myocardial infarction, stroke, transient ischemic attack, unstable angina, or coronary artery bypass surgery or other revascularization procedures within 12 months prior to screening * History or current diagnosis of ECG abnormalities indicating significant risk of safety for patients participating in the study- Known hypersensitivity to multiple drugs, monoclonal antibodies or other therapeutic protein * History of malignancy of any organ system (other than localized basal cell carcinoma of the skin or in situ cervical cancer), treated or untreated, within the past 5 years, regardless of whether there is evidence of local recurrence or metastases * Hepatic disease by history or total bilirubin ≥2×ULN or ALT or AST ≥3xULN as assessed by central laboratory at initial screening * History of severe constipation, defined as less than 3 bowel movements /week not adequately manageable by routine medical treatment, within 3 months prior to screening * Acute SARS-CoV2 Infection within 2 weeks prior to screening * Women who are pregnant or nursing * Known hypersensitivity to multiple drugs, monoclonal antibodies or other therapeutic proteins, or to erenumab or to any of the inactive ingredients * Unlikely to be able to complete all protocol required study visits or procedures, and/or to comply with all required study procedures (e.g., independent completion of electronic diary items) to the best of the patient's and investigator's knowledge * Prior known treatment with a CGRP receptor mAb (erenumab) * Prior treatment with a CGRP ligand antibody. Exceptions: Patients who participated in a randomized, placebo-controlled trial with CGRP ligand antibodies and were not unblinded (i.e., have no knowledge whether they received placebo or verum) can participate in the trial. Patients, who knowingly received a CGRP ligand antibody (i.e.galcanezumab or fremanezumab) can participate in the trial if the following criteria are met: a) Administered dose was not effective versus placebo in clinical trials i.e. galcanezumab (\<300 mg/month s.c.) or fremanezumab (≤675 mg loading dose followed by 225 mg s.c./month), b) Treatment duration of maximal 2 month or 2 injection cycles c) The last dose was administered at least 6 month prior to begin of screening epoche. * Patients who may be dependent on the sponsor or investigator * Patients who are in custody of an institution due to governmental authority decision or court order