In Brazil, inclusion and exclusion of health technologies within the Unified Health System (SUS) is the responsibility of the National Committee for Health Technology Incorporation (CONITEC). A recent Cochrane systematic review demonstrated that intramuscular interferon beta 1a (IFN-β-1a-IM) was inferior to the other beta interferons (IFN-βs) for multiple sclerosis (MS). As a result, CONITEC commissioned an analysis to review possible disinvestment within SUS. The objective of this paper is to describe the disinvestment process for IFN-β-1a-IM in Brazil. The first assessment comprised a literature review and mixed treatment comparison meta-analysis. The outcome of interest was the proportion of relapse-free patients in 2 years. This analysis confirmed the inferiority of IFN-β-1a-IM. Following this, CONITEC recommended disinvestment, with the decision sent for public consultation. More than 3000 contributions were made on CONITEC’s webpage, most of them against the preliminary decision. As a result, CONITEC commissioned a study to assess the effectiveness of IFN-β-1a-IM among Brazilian patients in routine clinical care. The second assessment involved an 11-year follow-up of a non-concurrent cohort of 12,154 MS patients developed by deterministic-probabilistic linkage of SUS administrative databases. The real-world assessment further demonstrated that IFN-β-1a-IM users had a statistically higher risk of treatment failure, defined as treatment switching or relapse treatment or death, with the assessment showing that IFN-β-1a-IM was inferior to the other IFN-βs and to glatiramer acetate in both direct and indirect analysis. In the drug ranking with 40,000 simulations, IFN-β-1a-IM was the worst option, with a success rate of only 152/40,000. Following this, CONITEC decided to exclude the intramuscular presentation of IFN-β from the current MS treatment guidelines, giving patients who are currently on this treatment the option of continuing until treatment failure. In conclusion, we believe this is the first example of this new disinvestment process in action, providing an exemplar for other treatments in Brazil as well as other countries.