以Hydroxyurea針對脊髓肌肉萎縮症進行一隨機、雙盲、安慰劑對照之臨床試驗

A Randomized, Double-blind, Placebo-controlled Trial of Hydroxyurea in Spinal Muscular Atrophy

陳泰亨(Tai-Heng Chen)

指導教授 ： 鐘育志

高雄醫學大學/醫學院/醫學研究所/碩士(2010年)

摘要

目的：
脊髓肌肉萎縮症（Spinal muscular atrophy, SMA），是一種會導致運動神經元漸進式退化的體隱性遺傳疾病，主要病因是由survival motor neuron（SMN1） 基因的缺損或突變造成完整功能的SMN 蛋白質減少所致，SMA患者身上常存在著一個以上的SMN2基因。人類兒童期發病之SMA臨床表現上可分為三型，分別為SMA第一型（嚴重型）、第二型（中間型）、第三型（輕型）。於利用藥物快速篩檢方式，發現hydroxyurea（HU）會使SMA患者之血液淋巴球細胞株增加SMN2 基因之全長型轉錄產物mRNA，可能是對SMA有療效的藥物。而先前研究發現，在使用不同劑量的HU於33位第二型與第三型SMA病患，為期8週的治療期接續8週的觀察期，發現受試者在肌力與血液中全長型SMN mRNA呈現些微改善之趨勢，所以此次我們進一步設計一隨機、雙盲、安慰劑對照之臨床藥物試驗來進一步確認HU在SMA患者之有效性及安全性。

研究方法：
在本計畫中，共募集63位SMA受試者，5位經篩選排除，符合納入臨床試驗條件受試者有58位，其中1位受試者因個人因素於開始服藥前退出，故納入參與臨床試驗之受試者共57位，28位為type II與29位type III，男女比為28：29，於2007年6月5日開始進行本臨床試驗。參與受試者隨機地被以2：1之比例分配為實驗組（HU）與對照組（安慰劑）。試驗期間HU一開始將以劑量10mg/kg/day方式給予，一個月後調升至 15mg/kg/day，滿兩個月試驗期後開始以20mg/kg/day給予一直到滿18個月的治療期。接續為停止藥物後的觀察期共六個月，試驗期間總共為期兩年。主要療效指標為粗動作功能評估量表（Gross Motor Function Measure, GMFM），徒手肌力測量（Manual Muscle Test, MMT），與血液中全長型SMN（full-length SMN, flSMN）轉錄產物(messenger RNA, mRNA)之表現量。次要療效指標為改良式Hammersmith運動功能量表（Modified Hammersmith Functional Motor Scale, MHFMS）與肺功能測試中的盡力最大吐氣量（forced vital capacity, FVC）。每位受試者除試驗開始時所做之基底值評估外，前兩個月每個月回診評估一次，之後每兩個月評估一次，兩年受試其間每位受試者總共接受14次評估。

研究結果：
共有55位受試者於2009年6月22日完成所有評估，期間有2位第二型 SMA男性受試者在本試驗中退出。與對照組相比，主要療效指標顯示在HU組的治療效益於粗動作功能評估量表為-1.88（p值為0.11），於徒手肌力測量為-0.55 （p值為0.49），於血液中全長型 SMN轉錄產物之表現量為2.17 （p值為0.13）；以上在均無統計學上之差異。相似地，進一步分析次要療效評估指標亦呈現兩組織間均無統計上之差異。此外，我們發現於兩年觀察期間，兩組的肺功能均呈現緩慢下降之趨勢但運動功能與肌力卻無甚變化。

結論：
以目前給予的HU劑量與時程，並無法於第二與第三型SMA病患身上的運動功能指標、肌肉力量、肺功能或是血液中的全長型 SMN mRNA 造成有意義的正面影響。然而，雖然結果無法達到所過去預期的效益，不過我們此試驗的設計與順利的於預期內完成，達成了世界上目前所有進行有關SMA臨床試驗中，為期最長（18個月的治療期加上後續6個月追蹤觀察期）且試驗期間追蹤次數最密集（共14次），因此我們追蹤過程所詳盡記錄的SMA病患評估，另一方面也呈現完整的SMA病患的自然病程演進的過程。

關鍵字

脊髓肌肉萎縮症 ； 雙盲性臨床試驗 ； 愛治 ； 運動功能指標 ； 轉譯醫學

並列摘要

Objectives:
Spinal muscular atrophy（SMA）is an autosomal recessive disorder due to progressive spinal motoneuron degeranation. It is caused by reduced levels of the intact survival motor neuron（SMN）protein as a result of deletion or mutation of the SMN1 gene. SMN protein is encoded by two genes, SMN1 and SMN2, which essentially differ by a single nucleotide in exon 7 leading to the majority of the transcript from SMN2 gene lacks an exon 7. According to clinical severity, childhood SMA was classified to three types, including type I, II, and III.
Hydroxyurea（HU）was found to be effective among the drugs we tested via a high throughput drug screen. It is capable of modifying the transcription pattern of SMN2 gene to increase the full-length of SMN mRNA expression. In an open-label pilot study with a design of 8-week treatment followed by another 8-week post-treatment observation, HU brought about slight improvements in strength and full-length SMN (flSMN) messenger RNA (mRNA) in 33 SMA patients. To confirm these findings, we designed a prospective two-year randomized, double-blind, placebo-controlled treatment/follow-up trial studying the efficacy and safety of HU to treat type II and III SMA patients evaluated every two months.

Methods:
In this study, we enrolled 63 SMA patients initially and 5 of them were excluded after screening. Among the 58 enrolled patients, one quitted spontaneously due to personal reason before the clinical trial started. Thus total 57 type II and type III SMA patients, with a male-to-female ratio of 28:29, were enrolled. Therefore, twenty-eight type II and twenty-nine type III SMA patients were randomized to receive HU or matching placebo in a 2:1 ratio. During the 18-month treatment, HU was initiated at 10mg/kg/day with an 8-week upward titration to 20mg/kg/day. The patients were assessed regularly during and 6 months after treatment. The primary outcome measures were the Gross Motor Function Measure (GMFM), Manual Muscle Test (MMT) and serum flSMN mRNA. The secondary outcome measures were the Modified Hammersmith Functional Motor Scale (MHFMS) and forced vital capacity (FVC) of lung function. Participants were evaluated 14 times.

Results:
Fifty-five patients completed this trial which lasted from March 2007 and June 2009. Except for neutropenia, we found no differences in adverse events between the two groups. Compared to placebo group, the HU group had -1.88 for GMFM (p = 0.11), -0.55 for MMT (p = 0.49) and 2.17 for flSMN mRNA (p = 0.13). Similarly, we found no difference in mean improvement of the secondary endpoints. Both group had a trend towards a declined FVC and little change in strength and motor function.

Conclusions:
Our results indicate that present dosage of HU for type II and III SMA patients did not significantly affect the global measures of motor functional scores, strength, lung function, or serum flSMN mRNA. However, during the course of finding these somewhat disappointing results, we performed a study that in more detail than most studies documents the longest running SMA double-blind trial, which included closely monitored patients during an 18-month drug treatment and 6-month post-treatment period. Further studies recruiting a larger SMA population with homogenous disease severity may help to clarify the clinical efficacy of HU.

並列關鍵字

Spinal muscular atrophy(SMA) ； double-blind clinical trial ； hydroxyurea(HU) ； motor function measures ； translational medicine

參考文獻

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