A small interfering RNA (siRNA) complementary to the region comprising a point mutation in the messenger RNA (mRNA) of the mutated human gene CLCN7, or derivative or precursor thereof, characterized in that: • the mutation is selected from one of the mutations resulting in the following mutations of the corresponding protein CIC-7: p.Y99C, p.D145G, p.W179X, p.G203D, p.L213F, p.G215R, p.P249L, p.R286W, p.R286Q, p.P470Q, p.R409W, p.L490F, p.G677V, p.688del, p.K689E, p.R762L, p.G765B, p.L766P, p.R767W, p.A788D, R223L, R223P, R223G, R223K, R223W, R223I, R223M, R223C, R223S, R265L, R265P, R265G, R265K, R265W, R265I, R265M, R265C, R265S, R271L, R271P, R271G, R271K, R271W, R271I, R271M, R271C, R271S, R280L, R280P, R280G, R280K, R280W, R280I, R280M, R280C, R280S, R281L, R281P, R281G, R281K, R281W, R281I, R281M, R281C, R281S, R286L, R286P, R286G, R286K, R286I, R286M, R286C, R286S, R326L, R326P, R326G, R326K, R326W, R326I, R326M, R326C, R326S, R362L, R362P, R362G, R362K, R362W, R362I, R362M, R362C, R361S, R403L, R403P, R403G, R403K, R403W, R403I, R403M, R403C, R403S, R405L, R405P, R405G, R405K, R405W, R405I, R405M, R405C, R405S, R409L, R409P, R409G, R409K, R409W, R409I, R409M, R409C, R409S, R436L, R436P, R436G, R436K, R436W, R436I, R436M, R436C, R436S, R526L, R526P, R526G, R526K, R526W, R526I, R526M, R526C, R526S, C211F, C211S, C211Y, C211R, C211G, C211W, C411F, C411S, C411Y, C411R, C411G, C411W, C438F, C438S, C438Y, C438R, C438G, C438W, W541R, W541S, W541L, W541G, W616R, W616S, W616L, W616G, L224S, L224P, L224W, L224H, L224Q, L224R, L224F, L224I, L224M, L224V, L224S, L224P, L224W, L224H, L224Q, L224R, L224F, L224I, L224M, L224V, L227S, L227P, L227W, L227H, L227Q, L227R, L227F, L227I, L227M, L227V, L564S, L564P, L564W, L564H, L564Q, L564R, L564F, L564I, L564M, L564V, S290Y, S290C, S290W, S290F, S290P, S290L, S290T, S290A, S290N, S365Y, S365C, S365W, S365F, S365P, S365L, S365T, S365A, S365N, S473Y, S473C, S473W, S473F, S473P, S473L, S473T, S473A, S473N, G241R, G241S, G241W, G241C, G241D, G241E, G241A, G241V, G347R, G347S, G347W, G347C, G347D, G347E, G347A, G347V, G361R, G361S, G361W, G361C, G361D, G361E, G361A, G361V; • that the siRNA has nucleotide sequence comprising a fragment of 15 to 25 nucleotides, containing the point mutation; • that the siRNA reduces the expression of the mutated protein CIC-7; • and that the ratio of efficacy of the siRNA in reducing the expression of mutated protein CIC-7 compared to the normal protein is greater than one • and wherein said derivative is characterized in that it comprises one or more chemically modified base that increases the stability and/or improves the efficiency and said precursor is a shRNA. • the mutation is selected from one of the mutations resulting in the following mutations of the corresponding protein CIC-7: p.Y99C, p.D145G, p.W179X, p.G203D, p.L213F, p.G215R, p.P249L, p.R286W, p.R286Q, p.P470Q, p.R409W, p.L490F, p.G677V, p.688del, p.K689E, p.R762L, p.G765B, p.L766P, p.R767W, p.A788D, R223L, R223P, R223G, R223K, R223W, R223I, R223M, R223C, R223S, R265L, R265P, R265G, R265K, R265W, R265I, R265M, R265C, R265S, R271L, R271P, R271G, R271K, R271W, R271I, R271M, R271C, R271S, R280L, R280P, R280G, R280K, R280W, R280I, R280M, R280C, R280S, R281L, R281P, R281G, R281K, R281W, R281I, R281M, R281C, R281S, R286L, R286P, R286G, R286K, R286I, R286M, R286C, R286S, R326L, R326P, R326G, R326K, R326W, R326I, R326M, R326C, R326S, R362L, R362P, R362G, R362K, R362W, R362I, R362M, R362C, R361S, R403L, R403P, R403G, R403K, R403W, R403I, R403M, R403C, R403S, R405L, R405P, R405G, R405K, R405W, R405I, R405M, R405C, R405S, R409L, R409P, R409G, R409K, R409W, R409I, R409M, R409C, R409S, R436L, R436P, R436G, R436K, R436W, R436I, R436M, R436C, R436S, R526L, R526P, R526G, R526K, R526W, R526I, R526M, R526C, R526S, C211F, C211S, C211Y, C211R, C211G, C211W, C411F, C411S, C411Y, C411R, C411G, C411W, C438F, C438S, C438Y, C438R, C438G, C438W, W541R, W541S, W541L, W541G, W616R, W616S, W616L, W616G, L224S, L224P, L224W, L224H, L224Q, L224R, L224F, L224I, L224M, L224V, L224S, L224P, L224W, L224H, L224Q, L224R, L224F, L224I, L224M, L224V, L227S, L227P, L227W, L227H, L227Q, L227R, L227F, L227I, L227M, L227V, L564S, L564P, L564W, L564H, L564Q, L564R, L564F, L564I, L564M, L564V, S290Y, S290C, S290W, S290F, S290P, S290L, S290T, S290A, S290N, S365Y, S365C, S365W, S365F, S365P, S365L, S365T, S365A, S365N, S473Y, S473C, S473W, S473F, S473P, S473L, S473T, S473A, S473N, G241R, G241S, G241W, G241C, G241D, G241E, G241A, G241V, G347R, G347S, G347W, G347C, G347D, G347E, G347A, G347V, G361R, G361S, G361W, G361C, G361D, G361E, G361A, G361V; • that the siRNA has nucleotide sequence comprising a fragment of 15 to 25 nucleotides, containing the point mutation; • that the siRNA reduces the expression of the mutated protein CIC-7; • and that the ratio of efficacy of the siRNA in reducing the expression of mutated protein CIC-7 compared to the normal protein is greater than one • and wherein said derivative is characterized in that it comprises one or more chemically modified base that increases the stability and/or improves the efficiency and said precursor is a shRNA.