OBJECTIVES In phase II studies, alirocumab, a PCSK9 inhibitor administered via subcutaneous injection, demonstrated significant reduction in LDL-C levels. The objective of this study was to conduct qualitative research to explore the concept of treatment acceptance in patients receiving a subcutaneous injection to support the development and testing of a patient-reported outcome measure, the Injection-Treatment Acceptance Questionnaire (I-TAQ). METHODS A literature review led to the targeting of ‘treatment acceptance’ as the measurement concept in preference to treatment satisfaction. Concepts generated from the literature and instrument review   informed the drafting of 17 items in the I-TAQ; item wording was adapted from three validated instruments. Qualitative interviews were conducted among 29 US-English speaking patients participating in alirocumab’s phase III program who self-administered the treatment via autoinjector (n=19) or pre-filled syringe (n=10). First, concept elicitation (CE) questioning was used to elicit concepts relating to patients’ treatment experiences and acceptance. The I-TAQ was then cognitively debriefed using “think-aloud” methods. Verbatim transcripts were analyzed using thematic analysis and Atlas.ti. Revisions were considered after each round of interviews. RESULTS Qualitative analysis of CE data indicated treatment acceptance to be high, with the following concepts identified as relevant: perceived efficacy, side effects, self-efficacy, convenience and overall acceptance. Ten (34%) patients reported an initial fear of needles, which subsided with no impact on discontinuation. Pain was not considered relevant by patients, suggesting no pain associated with the injection. Five items were added following round 1 interviews, three were retained after round 2 testing and two were added at finalization, forming the conceptually comprehensive 22-item I-TAQ. Patients demonstrated good understanding of item wording, instructions, response scales and recall period. CONCLUSIONS Successive rounds of interviews resulted in a treatment acceptance measure with strong content validity. Next steps are to psychometrically validate the I-TAQ in a population with experience of taking alirocumab.