Phenylketonuria: Current Treatments and Future Developments

페닐케톤뇨증의 치료: 현재와 미래

  • Lee, Jeongho (Department of Pediatrics, Soonchunhyang University Hospital)
  • 이정호 (순천향대학교 부속 서울병원 소아청소년과)
  • Published : 2020.12.31

Abstract

Phenylketonuria is the most prevalent disorder caused by an inborn error in aminoacid metabolism. It results from mutations in the phenylalanine hydroxylase (PAH) gene. If untreated or late treated, results in profound and irreversible mental disability. Newborn screening test identify patients with phenylketouria. The early initiation of a phenylalanine restricted diet very soon prevents most of the neuropsychiatric complications. However, the diet therapy is difficult to maintain and compliance is poor, especially in adolescents and adulthood. Since 2015, American Medical College of Medical Genetics and Genomics (ACMG) recommended more strong restrictive diet therapy for target blood level of phenylalanine (<360 umol/L). For over four decades the only treatment was a very restrictive low phenylalanine diet. This changed in 2007 with the approval of cofactor therapy (Tetrahydrobiopterin, BH4) which is effective in up to 30% of patients. Data from controlled clinical trials with sapropterin dihydrochloride indicate a similar occurrence of all-cause adverse events with this treatment and placebo. Large neutral aminoacids (LNAA) competes with phenylalanine for transport across the blood-brain-barrier and have a beneficial effect on executive functioning. A new therapy has just been approved that can be effective in most patients with PAH deficiency regardless of their degree of enzyme deficiency or the severity of their phenotype. Phenylalanine ammonia lyase (PAL-PEG) was approved in the USA by FDA in May of 2018 for adult patients with uncontrolled blood phenylalanine concentrations on current treatment. Nucleic acid therapy (therapeutic mRNA or gene therapy) is likely to provide longer term solutions with few side effects.

페닐케톤뇨증(PKU)은 전세계적으로 가장 잘 알려지고 중요한 유전성 대사질환이다. 1950년대 이후 단백제한을 이용한 식사치료를 처음으로 시도하여 성과가 있었던 질환이며 1960년대 이후 신생아선별검사를 통해 조기진단과 조기치료가 가능하게 된 최초의 유전성대사질환이기 때문이다. 단백제한 식사치료의 효과가 좋지만 학동기, 사춘기 이후 성인시기까지 유지하는 것의 어려움이 있고 이시기에 조절이 잘 되지 않았을 경우 경련, 여러가지 정신과적인 문제들, 삶의 질의 감소 등이 문제가 되어서 오랜 기간 치료를 위한 여러 방법들이 제시되었다. 더해서 2014년 미국의학유전학회(American Medical College of Medical Genetics and Genomics, ACMG)에서 전 연령에서 혈중 페닐알라닌 수치를 120-360 umol/L로 제시를 한 이후 더욱 치료의 중요성이 올라갔다. 2000년대 페닐알라닌수산화 효소(phenylalanine hydroxylase, PAH)의 조효소인 tetrahydrobiopterin (BH4)가 치료 승인되어서 약물반응을 보이는 환자에서 치료가 시작되었으며 4세미만에서도 허가가 되어서 이른 시기부터 약물치료를 병행하여 효과를 보게 되었다. 높은 혈중 페닐알라닌수치가 혈액-뇌 장벽(Blood-brain barrier, BBB)을 통하여 뇌로 넘어가서 회백질의 변성을 나타내게 되는 문제를 막기 위해 거대중성아미노산(LNAA)를 이용한 치료가 시도되고 있다. 오랫동안 연구되었던 페닐알라닌을 trans-cinnamic acid와 암모니아로 변화를 시키는 phenylalanine ammonialyase (PAL)을 이용한 효소치료는 최근 약제로 개발되어서 2018년 이후 성인환자를 대상으로 치료가 시작되었고 잘 조절되지 않는 환자들에게 효과를 보이고 있다. PAL을 경구용으로 개발하는 것이 빠르게 진행 중이며 유전자치료에 대한 연구들도 활발하게 진행이 되고 있어 다양한 치료들이 앞으로 기대된다.

Keywords

References

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