Recombinant human insulin-like growth factor I (rhIGF-I) for amyotrophic lateral sclerosis/motor neuron disease

Trophic factors, including recombinant human insulin-like growth factor I have been postulated as possible disease modifying therapies for amyotrophic lateral sclerosis. Randomised clinical trials of recombinant human insulin-like growth factor I in amyotrophic lateral sclerosis to date have yielded conflicting results.

The main objective of this review was to examine the efficacy of recombinant human insulin-like growth factor I in amyotrophic lateral sclerosis. Occurrence of adverse events has also been reviewed.

A search was carried out using the Cochrane Neuromuscular Disease Group register for randomised clinical trials of recombinant human insulin-like growth factor I in amyotrophic lateral sclerosis. Enquiries were also made of authors of randomised clinical trials as well as the manufacturers of recombinant human insulin-like growth factor I regarding any other randomised clinical trials which had not yet been published.

Types of studies: all randomised controlled clinical trials involving recombinant human insulin-like growth factor I treatment of amyotrophic lateral sclerosis.

Adults with a clinical diagnosis of definite or probable amyotrophic lateral sclerosis according to the El Escorial Criteria. Types of interventions: Treatment with recombinant human insulin-like growth factor I or placebo. Types of outcome measures: Primary: Change in Appel Amyotrophic Lateral Sclerosis Rating Scale (AALSRS) total score with 0.1mg/kg/day of recombinant human insulin-like growth factor I after nine months treatment. Secondary: Change in AALSRS with recombinant human insulin like growth factor I 0.1mg/kg/day and 0.05mg/kg/day at 1, 2, 3, 4, 5, 6, 7, 8, 9 months, change in quality of life (Sickness Impact Profile scale), survival and adverse events.

We identified two randomised clinical trials. Each reviewer graded them for methodological quality. Data were extracted and entered by the lead reviewer and checked by the other two. Some missing data had to be regenerated by calculations based on ruler measurements of data presented in published graphs.

The primary outcome measure was change in disease progression as determined by the Appel ALS Rating Scale total score with 0.1 mg/kg/day of recombinant human insulin-like growth factor I subcutaneously after nine months treatment. The level of significance was lower in the European trial which compared 59 patients on placebo with 124 on insulin-like growth factor I 0.1 mg/kg/day (weighted mean difference -3.30, 95%CI -8.68 to 2.08) than in the North American trial which compared 90 patients on placebo with 89 on recombinant human insulin-like growth factor I 0.05 mg/kg/day 89 patients and 87 patients on 0.1mg/kg/day (weighted mean difference -6.00, 95%CI -10.99 to -1.01). The combined analysis from both randomised clinical trials showed a weighted mean difference of -4.75 (95% CI -8.41 to -1.09) favouring the treated group. The secondary outcome measures showed similar trends favouring recombinant human insulin-like growth factor I but these did not reach significance at the five per cent level. Similarly the data with the 0.05mg/kg/day dose showed trends favouring recombinant human insulin-like growth factor I at all time points but did not reach significance at the five per cent level at any point. Evaluation of adverse events showed an increased risk of injection site reactions/inflammation with recombinant human insulin-like growth factor I (relative risk 2.53, 95% CI 1.40 to 4.59). The drug was otherwise safe and well tolerated.

Recombinant human insulin-like growth factor I may be modestly effective but the evidence currently available is insufficient for a definitive assessment. Further randomised clinical trials need to be done.