應用藥物基因體學於個人化Isoniazid劑量給予之 前瞻性臨床研究

Abstract

研究背景 Isoniazid(INH)在治療結核病當中扮演相當重要的角色，在前期具有快速殺菌活性，在後期可以保護rifampin(RIF)抗藥性的產生。因此，INH必須在全部療程中不間斷使用。高達90 % INH由N-acetyltransferase 2 (NAT2)酵素代謝成無活性代謝物。依目前研究可知NAT2有20餘種基因多型性，可分成三種表現型: 快速代謝型(RA)、中等代謝型(IA)、緩慢代謝型(SA)。根據過去文獻探討，SA族群相較於RA族群有28倍的風險產生肝功能不正常。然而在RA族群則是有較高的風險產生microbiological failure以及抗藥性產生，這樣的結果不會因為抗結核療程為合併藥物治療而有所改變。治療過程中產生副作用與抗藥性皆會影響結核病治療及INH使用的完整性。 研究目的 將依NAT2基因型個人化INH劑量的理論應用於臨床，且以藥物血中濃度監測為輔，分析出服藥後三小時INH目標濃度(C3hr)。此外臨床部分則評估安全性的追蹤結果與個人化INH劑量後的治療效果。希望藉由個人化INH劑量，提供不同基因型病人安全、完整且有效的治療。 研究材料與方法 本研究為前瞻性的臨床試驗，自2008年1月開始收案至2012年4月，由醫師轉介病人進入試驗。本試驗檢測病人NAT2基因型與INH血中濃度監測，綜合上述結果加上病人臨床狀況給予個人化INH劑量建議，最後由醫師端評估是否接受個人化INH劑量及是否接受後續INH血中濃度監測。本試驗使用PCR-RFLP進行基因型分析法，INH血中濃度部分則使用HPLC進行分析。 研究分析分為三部分:第一部份為INH血中濃度分析 : 將抽血時間限定於服藥後2.5-3.5小時的濃度點進行服藥劑量與INH血中濃度的分析。並以IA者服用INH 5 mg/kg/day對應的濃度做為標準濃度。第二部分為INH相關副作用分析 : 將使用INH大於30天的病人進行INH相關副作用(INH-related ADR)發生比率、嚴重程度與該ADR後續追蹤的分析，此外也探討INH相關副作用發生與INH血中濃度的關係。第三部分為療效分析 : 將確診為結核病並使用個人化INH劑量治療且在臺大醫院追蹤完畢的病人，評估結束治療前因任何原因INH中斷治療比例。 研究結果 進入第一部份血中濃度分析有32人(52個血中濃度點)，IA者服用目前治療指引建議之有效治療結核病的INH劑量 5 mg/kg/day，推估C3hr約為2 mcg/mL。SA者達到此目標濃度需要2.1 mg/kg/day；RA者達到此目標濃度需要6.3 mg/kg/day。第二部分INH相關副作用分析中，納入分析的39位病人特性為1. 年紀偏大(平均年齡: 67歲) 2. 肺外結核多(59 %) 3. 共病多( 85 %病人有一個以上的共病)。 在臨床追蹤過程發生12件INH相關副作用，其中2件為皮膚上副作用，其餘皆為藥物肝毒性。接受個人化INH劑量的7個事件，ADR緩解率為100 %；然而未接受個人化劑量建議的5個事件中，ADR緩解率只有40 %。發生INH相關藥物副作用的平均濃度為4.2±2.4 mcg/mL；而在治療過程中沒有發生INH相關藥物副作用的平均濃度為1.7±0.9 mcg/mL。第三部分分析使用個人化INH劑量的27位病人，INH中斷治療比例為0 %。然而臺大醫院資料庫顯示在同一時期臺大醫院在常規劑量下的病人，INH中斷治療比例為4.9 % (54/1108)。其中有63 %因為INH抗藥性、37 %是因為產生不可耐受之藥物副作用而使INH中斷治療。 結論 1. 依照本研究分析的結果，不同NAT2表現型中，INH使用劑量與INH血中濃度關係良好。 2. 在本研究中觀察到，病人發生INH相關副作用的組別C3hr是高於沒有發生INH相關副作用組別，該差距達統計上顯著意義。 3. 儘管本研究分析群屬於年紀較大且診治複雜性較高的病人，在本研究的結果顯示，經過適當地調整INH劑量，仍可降低ADR發生比率且INH中斷治療比率為0 %。 整體而言，依照NAT2基因型和病人體重個人化INH劑量，並輔以INH藥物血中濃度監測，可使INH在所有病人可持續使用至結束治療。使INH這個在結核病治療中相當重要的藥品，可以更安全、有效且完整的發揮其治療地位。

Background Isoniazid (INH) plays an important role in the treatment of tuberculosis infection. INH is responsible for early bactericidal activity in the intensive phase and prevention of rifampin resistance in the continuous phase of the treatment. Therefore, INH should be used continuously during the whole treatment course. N-acetyltransferase 2 (NAT2) dominates the metabolism of INH and it has been reported that there are more than twenty NAT2 single nucleotide polymorphisms (SNPs). People can be classified into three NAT2 phenotypes, rapid acetylators (RA), intermediate acetylators (IA), and slow acetylators (SA), based on the number of wild type alleles of NAT2 (SNPs).According to the literature review, SA are under higher risk of drug induced liver injury than RA group. On the other hand, RA are under higher risk of microbiological failure and INH resistance and which is still significant in the multiplicity of an anti-tuberculosis regimen. The occurrence of resistance and adverse drug reaction would influence the completeness of INH in the treatment. Objectives To adapt the theory of individualized dosing of INH into clinical practice by NAT2 polymorphism and 3 hours post-dose (C3hr) concentration of INH was the primary objective. In addition, the safety and clinical outcome issues were evaluated during the follow-up period in this study.

Materials and Methods This study was conducted prospectively and patients were referred from physicians. Individualized INH dosing was suggested according to NAT2 genotype, INH serum concentration, and clinical situation. NAT2 genotyping and INH serum concentration were performed by polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP) and high performance liquid chromatography (HPLC), respectively. There were three parts in data analysis. The first part was INH serum concentration analysis: the correlation between C3hr of INH and NAT2 polymorphism. We used the average C3hr of INH from IA at 5 mg/kg/day as the target C3hr of INH for SA and RA. The second part was INH-related ADR and C3hr of INH analysis. We analyzed the INH-related ADR occurrence rate, severity and follow up in safety assessment. The third part was the interruption rate of INH for any cause before end of treatment as the primary outcome in clinical outcome assessment. Results There were 32 cases (52 samples) for the INH serum concentration analysis. The average C3hr of INH in IA at dose of 5 mg/kg/day was about 2 mcg/mL. When SA and RA took 2.1 mg/kg/day and 6.3 mg/kg/day of INH, respectively, they could reach the target INH serum concentration according to our results. The characteristics of our 39 patients analyzed in the second part were elder with more comorbidities, and more extrapulmonary TB patients. There were 12 INH-related ADR events occurred during the follow-up period. Among them, 10 events were drug induced liver injury (DILI) and 2 events were cutaneous adverse drug reaction. Of 7 events underwent individualized dosing of INH, the ADR relief rate was 100 %. But the ADR relief rate was only 40 % in the conventional dosing group of 5 patients. Mean INH serum concentrations in patients with INH-related ADR and those with no INH-related ADR were 4.2±2.4 mcg/mL and 1.7±0.9 mcg/mL, respectively, in this study (P<0.05). INH interruption rate was 0 % (0/27) in the individualized dosing cases compared to 4.9% (54/1108) interruption in conventional dosing patients at National Taiwan University Hospital due to INH resistance and intolerable ADR before the end of treatment during 2008/1/1 to 2012/4/30. Conclusions 1. According to our results , a good correlation between C3hr of INH and NAT2 polymorphisms was observed. 2. The occurrence of INH-related ADR was observed in patients with higher C3hr of INH compared to those without INH-related ADR. 3. Although patients were older and more complicated in our study, no INH interruption and decreased ADR rate were found in our patients with appropriate dose adjustment of INH Overall, INH can all be continuously used throughout the treatment course by individualized dosing of INH successfully in this study. It improves the safety and completeness of this important drug in the treatment of TB.