Purpose: Although studies have shown the efficacy of laquinimod (LAQ) on disease progression in patients with multiple sclerosis (MS), there is some controversy about whether it improves the types of outcomes and side effects. The main purpose of the present study was to systematically review and meta-analyze the efficacies and side effects of LAQ in patients with relapsing-remitting MS (RRMS).

Methods: PubMed, Scopus, and Web of Science databases were searched with relevant keywords for articles published up to June 2019. Six randomized control trials that examined LAQ vs. placebo in adult patients with MS were included. Information on the effectiveness and side effects of LAQ were extracted. The quality of the included studies was appraised using Jadad scores, and the data were divided into subgroups according to different doses and periods.

Results: Efficacy of LAQ: The number of Gadolinium-enhancing (GDE) lesions significantly decreased after treatment with LAQ (SMD = -0.15, 95% CI: -0.23, -0.07), but there was no significant reduction in the number of T2 lesions (SMD = -0.38, 95% CI: -1.04, 0.28). The relapse rate (SMD = -0.13, 95% CI: -0.21, -0.04) and MS Functional Composite (MSFC) score significantly decreased with LAQ treatment (SMD =0.14, 95% CI: 0.05, 0.23). Risk of adverse events: The risk of diarrhea, nausea, abdominal pain, and all adverse events did not significantly increase (p > 0.05) with treatment with LAQ; however, the risk of back pain, headache, and vomiting significantly increased (p < 0.05). The change in mortality rate was not significant (OR = 0.25, 95% CI: 0.04, 1.50).

Conclusions: LAQ can considerably improve clinical and imaging outcomes in RRMS patients. The most effective dose of LAQ with lower side effects may be 0.6 mg/day for at least 2 years, but more evidence is needed to confirm these results.Laquinimod can improve clinical and imaging outcomes in patients with multiple sclerosis.Back pain and headache are probable side effects of laquinimod in patients with multiple sclerosis.The most effective and safe dose of laquinimod for patients with multiple sclerosis may be 0.6 mg/day for 2 years.