Extension Study of ABP-20001 to Evaluate Safety and Efficacy of Repeat Treatments of ABP-450 for Migraine Prevention

Inclusion Criteria: 1. Patient can understand the ICF, provides signed ICF and patient privacy information (eg, Authorization for Use and Release of Health and Research Study Information) before initiating any study-specific procedure, and agrees to comply with protocol requirements. 2. Patient was enrolled in Study ABP-20001 and successfully completed that study's treatment and procedures. 3. A WOCBP must be willing and able to use a medically acceptable and effective method of birth control, as determined by the investigator, during the entire study. 4. A WOCBP must have a negative urine pregnancy test at Visit 1. 5. Patient can read, understand, and complete the eDiary. 6. Patient is willing and able to adhere to the study assessments, visit schedules, and prohibitions, as described in this protocol. Exclusion Criteria: 1. Did not meet eligibility criteria for Study ABP-20001 and was improperly enrolled or randomized in that study. 2. Failure to successfully complete the Study ABP-20001, including the following: 1. use of prohibited medications 2. delay of \>4 weeks in receiving second Study ABP-20001 investigational study drug injection 3. completing fewer than 75% of eDiary entries during the 28-week treatment and follow-up periods 4. 7 or more consecutive missed days of eDiary entries Note: if the investigator determines that any of the above 4 failures occurred due to extenuating circumstances, patients may be allowed to enroll in Study ABP-20002 if the investigator expects the problem will not recur. Medical Conditions: 3. History of migraine accompanied by diplopia or decreased level of consciousness, or retinal migraine. 4. Current diagnosis of chronic tension-type headache, new persistent daily headache, trigeminal autonomic cephalgia (eg, cluster headache), or cranial neuropathy. 5. Confounding and clinically significant pain syndromes (eg, fibromyalgia, chronic low back pain, complex regional pain syndromes) as evaluated by the investigator. 6. Diagnosis of myasthenia gravis, Lambert-Eaton syndrome, amyotrophic lateral sclerosis, or any other significant neuromuscular disease that might interfere with the study. 7. Psychiatric conditions that are uncontrolled and/or untreated as evaluated by the investigator. 8. Lifetime history of psychosis, mania, or dementia. 9. History of addiction, including alcohol or drug abuse since initiating ABP-20001 study treatment. 10. Any infection or clinically significant skin problem in any of the injection sites. 11. Any medical condition (including but not limited to viral or other active infections) that, in the opinion of the investigator, classifies the patient as unsuitable for participation in the study or patients who do not seem to be in good general health at the time of signing the ICF, and prior to any investigational study drug administration. Note: Patients will not routinely be tested for COVID-19 during the study. Patients presenting with fever or who are symptomatic for COVID-19 will be required to be tested and treated through their general practitioner. Other Diagnostic Assessments: 12. Significant risk of self-harm based on clinical interview and responses on the C-SSRS, or of harm to others in the opinion of the investigator; patients must be excluded if they report suicidal ideation with intent, with or without a plan (ie, Type 4 or 5 on the C-SSRS) in the time since enrolling in Study ABP-20001. Prior/Concomitant Medications and Treatments 13. Injection with anesthesia or steroids in the targeted muscles since initiating ABP-20001 study treatment. 14. Use of opioids or barbiturates \>2 days per month since initiating ABP-20001 study treatment. 15. Use of CBD or other types of cannabinoids since initiating ABP-20001 study treatment. 16. Use of botulinum toxin for migraine or any other medical reasons, including cosmetic use, at or above the shoulders outside of Study ABP-20001 since initiating ABP-20001 study treatment and throughout Study ABP-20002. 17. Any CGRP inhibitor treatment (eg, erenumab \[Aimovig®\], eptinezumab \[Vyepti®\], fremanezumab \[Ajovy®\], or galcanezumab \[Emgality®\], rimegepant sulfate \[Nurtec™\], ubrogepant \[Ubrelvy™\] within or outside of a clinical study) since initiating ABP-20001 study treatment. 18. Use of small molecule migraine drugs (eg, beta-blockers, anticonvulsants, antidepressants, calcium channel blockers) since initiating ABP-20001 study treatment. 19. Use of devices for the treatment of migraine (ie, non-invasive neuromodulation therapies including but not limited to non-invasive nerve stimulation \[gammaCore\], transcranial magnetic stimulation \[Cefaly\], external trigeminal nerve stimulation, transcutaneous electrical nerve stimulation, and peripheral neuroelectrical stimulation) since initiating ABP-20001 study treatment. 20. Any other treatments or therapies (eg, acupuncture in head and neck region, cranial traction, nociceptive trigeminal inhibition, occipital nerve block treatments, and dental splints for headache) to the head, neck, or shoulder regions since initiating ABP-20001 study treatment that, in the opinion of the investigator, would interfere with the investigational study drug. 21. History of inadequate response to 3 classes of medications (which have different mechanisms of action) prescribed for the prevention of migraine, excluding CGRP therapies. 22. History of hypersensitivity to human serum albumin, sucrose, or botulinum toxin type A. 23. Participation in another interventional study since initiating ABP-20001 study treatment. Other Exclusion Criteria: 24. Patients who have been infected with COVID-19 for whom the infection worsened their migraine disorder. Patients for whom infection with COVID-19 did not worsen their migraine disorder may be included in the study. 25. Female patients pregnant or planning on becoming pregnant during the study and/or lactating/breastfeeding. 26. Patient is an employee or family member of the investigator, study site personnel, PPD, or AEON.