Targets in ALS: designing multidrug therapies Maria Teresa Carrı ` 1,2 , Giuliano Grignaschi 3 and Caterina Bendotti 3 1 Department of Biology, University of Rome Tor Vergata, Via della Ricerca Scientifica, Rome 00133, Italy 2 Fondazione Santa Lucia, Centro Europeo di Ricerca sul Cervello, Via del Fosso di Fiorano 64, 00143 Rome, Italy 3 Department of Neuroscience, Istituto di Ricerche Farmacologiche Mario Negri, Via Eritrea 62, 20157 Milan, Italy Amyotrophic lateral sclerosis (ALS) is an incurable disease that arises from the progressive loss of motoneurons. Even when caused by a single gene defect, as in the case of mutations in the enzyme Cu– Zn superoxide dismutase (SOD1), ALS is the result of a complex cascade that involves crosstalk among moto- neurons, glia and muscles, and evolves through the action of converging toxic mechanisms. Transgenic rodents that express human mutant SOD1 and develop a progressive paralytic disease are widely used to screen potential therapeutics. Treatments that interfere with a specific event in the neurotoxic cascade have been reported to produce a modest increase in rodent lifespan. Multi-intervention approaches, including novel methods to intercept the damage and to deliver molecules to vulnerable cells, have recently been shown to be more effective. Thus, new avenues for promising therapeutic approaches can be derived from multidrug treatments and/or the delivery of growth factors by viral vectors, in combination with exercise and/or diet regimens. Amyotrophic lateral sclerosis: an elusive pathology Amyotrophic lateral sclerosis (ALS) is a fatal disorder that is characterized by the selective loss of upper and lower motoneurons and by progressive muscle atrophy. ALS is one of the most common neurodegenerative disorders, with a prevalence of between four and six per 100 000, and it occurs in sporadic (sALS) and familial (fALS) forms. The best-known cause of ALS, which is responsible for 1/5 of the cases of fALS, is a mutation in the gene that encodes the enzyme Cu–Zn superoxide dismutase (SOD1), a well-characterized enzyme that is abundant in the cytoplasm and mitochondria of virtually every cell type. Almost 120 different SOD1 point mutations have been reported in families with ALS (http://www.alsod.org) but the mechanism (or mechanisms) through which mutant SOD1 (mSOD1) enzymes produce the pathological pheno- type is still debated [1,2]. In 2001, Turner et al. [3] listed w50 different medications that have been tested for the treatment of ALS since 1941, all but one of which had no effect on patient survival. More trials have been conducted since 2001, although they have also been ineffective (an extensive list can be found at http://www.als.net/). Riluzole, which is the only drug currently registered for ALS, prolongs survival by only approximately three months and it does not clearly improve the quality of life or muscle strength of patients [4]. The reasons for the inefficacy of past clinical trials for ALS might reside in problems with their design [5] or in the incomplete knowledge of the mechanisms by which motoneurons die in ALS. These mechanisms have been studied in different experimental paradigms and in postmortem samples from patients. In this article, we focus on how data obtained using animal models of SOD1-linked fALS have prompted novel therapeutic approaches that are aimed at prevent- ing damage to motoneurons and their neighbouring cells, and suggest a rationale for a multidrug intervention. Animal models of ALS The discovery of mutations linked with fALS has made possible the development of aetiological models of the disease (Table 1). Several transgenic mouse and rat strains were created by the introduction of the sequence coding for human mSOD1 under the control of a promoter that enables ubiquitous expression of the transgene [6]. Unlike SOD1 knockouts, transgenic mice and rats with human fALS–SOD1 added to their own enzyme have a phenotype that closely resembles ALS (i.e. adult-onset progressive motor paralysis, muscle wasting and reduced lifespan). They also express almost all of the essential histopathological features of the human disease, including the selective degeneration of motoneurons in the spinal cord, the presence of ubiquitinated protein aggregates in motor axons and motoneuron perikarya, in addition to the fragmentation of the Golgi apparatus in motoneurons and the activation of microglia and astrocytes in the spinal cord and brainstem [6]. Moreover, several biochemical alterations observed in patients – such as the appearance of oxidative-stress markers, alterations of mitochondria in motoneurons and muscle and the activation of phos- phorylation cascades – are, in most cases, preserved in these models [1]. There are, however, some differences between the various mSOD1 mouse strains [2] and, depending on the mutation and copy number of the transgene, mSOD1 transgenic rodents die aged between four and 14 months (Table 1). Transgenic mice that overexpress the human SOD1G93A are the most widely used model for therapy development. This strain, which Corresponding author: Bendotti, C. (bendotti@marionegri.it). Review TRENDS in Pharmacological Sciences Vol.27 No.5 May 2006 www.sciencedirect.com 0165-6147/$ - see front matter Q 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.tips.2006.03.009