naltrexone hydrochloride delayed-release

SP-104 is a novel, proprietary, fixed dose, delayed burst release formulation of low-dose naltrexone hydrochloride (4.5 mg) being developed for the treatment of fibromyalgia. This formulation aims to reduce side effects associated with immediate release naltrexone while addressing fibromyalgia disease burden[2]. The drug has completed Phase 1 clinical trials, which demonstrated that healthy volunteers treated with SP-104 had lower rates of adverse events compared to those treated with immediate release naltrexone[2]. This is particularly significant given the large number of fibromyalgia patients (estimated 10 million in the U.S. and more than 200 million worldwide) and the high provider dissatisfaction with existing approved treatments[2]. Currently, there are no low-dose formulations of naltrexone (less than 5 mg) commercially available. Physicians typically use high-dose tablets (50 mg) and have compounding pharmacies prepare lower doses, which can lead to dosing inaccuracies and quality concerns[2]. Scilex Holding Company, a Sorrento company, is developing SP-104 and intends to initiate Phase 2 studies. If successful, SP-104 could become a pivotal treatment for fibromyalgia, representing a large commercial opportunity with high unmet needs[2][5]. As of May 2025, SP-104 appears to be in clinical development, with Phase 1 trials completed in the second quarter of 2022[5].

Other names

low-dose naltrexone hydrochloride delayed-release