Inclusion Criteria:

• possible, probable (clinically or laboratory) or definite ALS according to the revised version of the El Escorial World Federation of Neurology criteria
• disease duration more than 6 months and less than 3 years
• best-sitting FVC between 50% and 95% of predicted normal
• continuously treated with 100 mg riluzole daily, for at least one month
• onset of progression weakness within 36 months prior to study
• women of childbearing age be non-lactating and surgically sterile or using a highly effective method of birth control and have a negative pregnancy test
• capable of thoroughly understanding all information given and giving full informed consent according to GCP

Exclusion Criteria:

• previous participation in another clinical study within the preceding three months
• tracheotomy or assisted ventilation of any type during the preceding three months
• gastrostomy
• any medical condition known to have an association with motor neuron dysfunction which might confound or obscure the diagnosis of ALS
• presence of any concomitant life-threatening disease or impairment likely to interfere with functional assessment
• confirmed hepatic insufficiency or abnormal liver function (ASAT and/or ALAT more than 1.5 upper limit of normal)
• renal insufficiency (serum creatinine more than 2.26 mg/dl)
• evidence of major psychiatric disorder or clinically evident dementia precluding evaluation of symptoms
• known hypersensitivity to any component of the study drugs
• likely to be not cooperative or comply with the trial requirements (as assessed by the investigator), or unable to be reached in the case of an emergency
• other antidiabetics
• heart failure or heart failure in the patients history (NYHA I to IV)
• history of macular oedema
• treatment with thiazolidinediones within 3 months prior to screening
• known or suspected history of alcohol and/or drug abuse
• treatment with gemfibrozil within 3 months prior to screening