34 Lee SH, et al. 와는달리단독투여에비해 PTH의골형성효과가오히려감소되었고, 골양증가에대한상승효과도관찰되지않았다 [5,6]. 비스포스포네이트병용시에 PTH에의한골형성작용이감소되는기전으로골재형성과정중에골흡수와골형성이순차적으로일어난다는짝짓기현상이제시되고있는데,

Transcription

1 Endocrinol Metab 26(4):33-39, December 211 ORIGINAL ARTICLE 골다공증동물모델에서골밀도변화에관한카텝신 K 억제제와부갑상선호르몬병용요법의효과 이승훈 고정민 이영선 1 김범준 최제용 2 김기수 울산대학교의과대학서울아산병원내분비대사내과, 아산생명과학연구소 1, 경북대학교의과대학생화학 세포생물학교실 2 The Effects of Combination Therapy of Cathepsin K Inhibitor and PTH on Change in Bone Mineral Density in an Animal Model of Osteoporosis Seung Hun Lee, Jung-Min Koh, Young-Sun Lee 1, Beom-Jun Kim, Je-Yong Choi 2, Ghi-Su Kim Division of Endocrinology and Metabolism, Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul; Asan Institute for Life Sciences 1, Seoul; Department of Biochemistry and Cell Biology 2, Kyungpook National University School of Medicine, Daegu, Korea Background: We hypothesized that combination therapy of cathepsin K inhibitor (CTKi) and human parathyroid hormone (1-34) (teriparatide, PTH) would overcome the coupling phenomenon of bone resorption and formation and thus may rapidly increase bone mass. Methods: We selected a dose of zoledronic acid (ZA) that had shown similar effects with CTKi on body bone mineral density (BMD) change during the preliminary experiment. Female mice were subjected to ovariectomized (OVX control) or a sham operation (SHAM group). The mice were treated with CTKi (CTKi group), ZA (ZA group), PTH (PTH group) or with a combination of PTH with ZA (ZA PTH group) or CTKi (CTKi PTH group) for 8 weeks. Total BMD was measured before the operation and at 4 and 8 weeks. Results: In the preliminary results, 1 μg/kg of ZA showed similar BMD changes with CTKi. Compared with the OVX control, BMD in the SHAM, ZA, CTKi, PTH, ZA PTH, and CTKi PTH groups was significantly increased after treatment. BMD in the CTKi PTH group, but not in the ZA PTH group increased more significantly than in the PTH group at the end of treatment. Compared with the OVX control, changes in BMD in the SHAM, ZA, CTKi, PTH, ZA PTH, and CTKi PTH groups increased significantly after 8 weeks of treatment. The change in BMD in the CTKi PTH group, but not in the ZA PTH group was more significantly increased than the change in BMD in the PTH group. Conclusion: When combined with PTH, CTKi augmented the anabolic action of PTH. Therefore, combination therapy with CTKi and PTH might be a new therapeutic modality capable of overcoming the coupling phenomenon, thereby markedly and rapidly increasing bone mass. (Endocrinol Metab 26:33-39, 211) Key Words: Bisphosphonate, Cathepsin K inhibitor, Combination therapy, Coupling phenomenon, Parathyroid hormone 서론 골다공증은골강도의약화로골절이증가하게되는골격계질환이다 [1]. 폐경후골소실과골교체율이급격히증가하면서골다공증이발생하게된다 [2,3]. 현재쓰이고있는골다공증치료제는기전 Received: 15 March 211, Accepted: 14 July 211 Corresponding author: Jung-Min Koh Division of Endocrinology and Metabolism, Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Pungnap 2-dong, Songpa-gu, Seoul , Korea Tel: , Fax: , jmkoh@amc.seoul.kr 본연구는대한내분비학회 24 년젊은연구자상, 29 년젊은연구자상의지원에의하여이루어진것임. 으로볼때크게골흡수억제제와골형성촉진제로나눌수있다 [4]. 골흡수억제제인비스포스포네이트와골형성촉진제인간헐적부갑상선호르몬 (1-34) (teriparatide, PTH) 주사간의병용요법은골흡수를감소시키는동시에골형성을증가시킬수있어각각의단일제제에비해더많은골양의증가를가져오리라기대되었으나기대 Copyright 211 Korean Endocrine Society This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

2 34 Lee SH, et al. 와는달리단독투여에비해 PTH의골형성효과가오히려감소되었고, 골양증가에대한상승효과도관찰되지않았다 [5,6]. 비스포스포네이트병용시에 PTH에의한골형성작용이감소되는기전으로골재형성과정중에골흡수와골형성이순차적으로일어난다는짝짓기현상이제시되고있는데, 비스포스포네이트에의해골흡수가억제되어연차적으로골형성이억제된다는것이다 [7]. 최근에카텝신 K 억제제 (cathepsin K inhibitor, CTKi) 가새로운골흡수억제제로개발되고있는데, 카텝신 K (cathepsin K, CTK) 는파골세포에서만선택적으로발현되는중요한시스테인단백분해효소로골흡수에중요한역할을한다 [8]. CTKi는시험관내에서나생체내에서골흡수를억제하였으며 [9,1], 실제약물로개발이되어임상시험이진행되고있다 [11,12]. 흥미로운점은 CTKi가생체에서골형성의심각한억제를유발하지않았다는점인데 [11-16], 이러한결과들은 CTK를억제시골흡수와골형성간의짝짓기현상이일어나지않아골흡수가감소함에도불구하고골형성은이루어질수있음을시사한다. 본연구는 CTKi를 PTH와병용시에골양증가에대한추가적이거나상승작용이나타나리라는가정하에, 경구용 CTKi인 OST-477 (furan-2-carboxylic acid, 1-{1-[4-Fluoro-2-(2-oxo- pyrrolidin-1-yl)-phenyl]-3-oxopiperidin-4-ylcarbamoyl}-cyclohexyl)- amide) [17] 과 PTH의병용요법이골흡수와골형성간의짝짓기현상을극복하여골양을급격하게증가시킬수있는지알아보고자기획되었다. 대상및방법 1. 시약과실험동물 CTK 효소활성도측정키트 (AnaSpec, San Jose, CA, USA), 졸레드론산 (ZA; Norvatis, Basel, Switzerland), PTH (Eli Lilly and Company, Indianapolis, IN, USA) 를구입하였고, 동아제약과유한양행연구소에서경구용 CTKi인 OST-477 (Dong-A Parmaceutical, Yuhan Co., Seoul, Korea) 을제공받았다. 8주령의암컷 C57BL/6 생쥐를오리엔트사 (Orient Bio Inc., Seongnam, Korea) 에서구입하여실험종료시까지온도 (22 ± 2 C) 와명암 (12시간주기 ) 을조절한환경에서표준식이 (Purina Mills, St. Louis, MO, USA) 를섭취시키며사육시켰다. 12주령에복강으로 ketamine (48 mg/kg) 과 xylazine (5.6 mg/kg) 을투여하여난소절제술이나가짜수술을시행하였다. 모든실험은울산대학교아산생명과학연구소동물실험위원회방침및동물실험관련법규를따라모든실험을진행하였다. 2. CTK 효소억제도분석 CTKi인 OST-477 의사람 CTK에대한효소억제도분석을상용화된키트를이용하여제조사의프로토콜에따라측정하였다 [18]. 간 단히서술하면, 사람 CTK의기질은 2.5 mm Z-Phe-Arg-AMC (AMC: 7-Amino-4-methyl coumarin) 를사용하며최종반응버퍼의구성은 ph 5.5인 4 mm sodium acetate buffer, 2 mm cysteine, 5 mm EDTA로되도록하였다. 반응억제의시작을위하여최종반응버퍼에기질과억제제의혼합물을첨가하여 37 C에서 1시간동안배양하였다. 기질의가수분해의정도는 SPECTRAmax GEMINI-XS Microplate Spectrofluorometer (Molecular Devices, Sunnyvale, CA, USA) 를이용하여흥분과방출도를각각 353과 442 nm에서흡광도를측정하였다. 반응이억제되는정도 (%) 는불활성매개체를포함한대조반응과비교하여계산하였다. 3. 예비동물실험난소절제골소실유발골다공증동물모델에서 OST-477의골흡수억제효과와유사한 ZA의용량을찾고, ZA가 PTH의반응을약화시키는지에대해다음과같은예비연구를실시하였다. 생쥐를 12주에가짜수술 (sham operation, SHAM군, n = 5) 및난소절제 (ovariectomized, OVX) 를시행하였다. 난소를절제한생쥐들은여덟군으로나누었는데, 각각위약을투여한군 (OVX 대조군, n = 5), OST mg/kg [17] 을하루 2번매일경구로투여한군 (CTKi, n = 5), ZA 1 μg/kg (ZA1, n = 5) [19], 2 μg/kg (ZA2, n = 5) [2] 을복막으로한번투여한군, ZA 1 μg/kg을복막으로 1회투여하고 PTH 1 μg/kg (ZA1 PTH1군, n = 5) 혹은 2 μg/kg을피하로하루한번투여한군 (ZA1 PTH2군, n = 5) [21], ZA 2 μg/kg 을복막으로 1회투여하고 PTH 1 μg/kg (ZA2 PTH1군, n = 5) 혹은 2 μg/kg을피하로하루한번투여한군 (ZA2 PTH2군, n = 5) 이었다 [21]. 약물투여는수술후 1주일뒤 (13주령 ) 부터시작하였으며, 체중과전체골밀도는수술전과치료시작후 4주후에측정하며심장천자를하여희생시켰다. 희생시자궁위축의발생을관찰함으로써난소절제가성공적으로이루어졌음을확인하였다. 4. 본동물실험생쥐를 12주에가짜수술 (SHAM군, n = 8) 및난소절제를시행하였다. 난소를절제한생쥐들은여섯군으로나누었는데, 각각위약을투여한군 (OVX 대조군, n = 8), ZA 1 μg/kg을복막으로한번투여한군 (ZA군, n = 8), OST mg/kg을하루 2번매일경구로투여한군 (CTKi군, n = 8), PTH 1 μg/kg 을경피로매일투여한군 (PTH군, n = 8), ZA 1 μg/kg을복막으로 1회투여하고 PTH 1 μg/ kg을피하로하루한번투여한군 (ZA PTH군, n = 8), OST mg/kg을하루 2번매일경구로투여하고 PTH 1 μg/kg을피하로하루한번투여한군 (CTKi PTH군, n = 8) 이었다. 약물의투여는수술후 1주일뒤 (13주령 ) 부터시작하여 8주간지속하였으며, 체중과전체골밀도는수술전과매 4주마다측정하며심장천자를하여희생시켰다. 희생시자궁위축의발생을관찰함으로써난소절

3 Effects of Combination Therapy of Cathepsin K Inhibitor and PTH on BMD Change 35 제가성공적으로이루어졌음을확인하였다. 5. 골밀도측정전체골밀도는 Lunar PIXImus densitometer software version (GE-Lunar Co., Madison, WI, USA) 로측정하였으며, 1개의다른쥐를 3번측정하였을때에분산계수 (coefficient of variation) 는 1.27% 이었다. 6. 통계분석모든측정의결과들은평균 ± 표준편차혹은평균과 95% 신뢰구간 (confidence interval, CI) 로표시하였고, 각군간의변수차이는세군이상의모수적검정은 one way analysis of variance (ANOVA) 및 Tukey s multiple comparison test를이용하여분석하였다. 통계적분석은통계분석소프트웨어 SPSS version 12. (SPSS Inc., Chicago, IL, USA) 를이용하였고, P <.5인경우를유의한경우로판단하였다. 결과동물에투여하기전에실제로 CTK를억제하는지확인하기위한효소억제도분석에서 OST-477은사람 CTK를대조군에비해약 41.9 ± 9.8% 억제함을확인하였다 (Fig. 1). 예비실험에서체중은수술전모든군에서유사하였으나, 수술후 4주뒤에 SHAM군 (19.7 ±.4 g) 은난소절제술을받은다른군들에비해유의하게덜증가하였다 (P =.1) (Table 1). 골밀도는수술전모든군에서차이가없었으나, 치료후에는 OVX 대조군에비해 SHAM군 (P =.1), ZA1군 (P =.13), ZA2군 (P <.1), ZA1 PTH1 군 (P <.1), ZA1 PTH2 군 (P <.1), ZA2 PTH1 군 (P <.1), ZA2 PTH2 군 (P <.1) 에서유의하게 증가하였으며, CTKi 군에서도증가하는경향을보였다 (P =.88) (Table 1). CTKi 투여시와유사한골밀도변화를보인 ZA 군은 ZA1 군으로 CTKi 군과의차이가 1.8% (95% CI, -3.8 to 7.3) 로유의한차이 가없어본실험에서는 ZA 1 μg/kg 을투여하기로결정하였다 (Fig. 2). 또한, ZA 1 μg/kg 에 PTH 1 μg/kg 혹은 2 μg/kg 을병용투여 할때에 ZA1 군에비해각각 2.6% 혹은 4.4% 의증가가있었으며, ZA 2 μg/kg 에 PTH 1 μg/kg 혹은 2 μg/kg 을병용투여할때에 ZA2 군에비해각각 2.4% 혹은 4.8% 의증가를보였다 (Fig. 2). 따라 서, ZA 에의해 PTH 의골형성작용이둔화되는효과를보기위한 PTH 의용량을 1 μg/kg 으로투여하기로결정하였다. 본실험에서는 Fig. 3 에서보이는것처럼체중은수술전모든군에 서유사하였으나, SHAM 군이수술후 4 주뒤에 21.6 ± 1.5 g 으로덜 증가하는경향을보였으며 (P =.93), 연구종료시점에서는 23.4 ± 1.5 g 으로유의하게덜증가하였다 (P <.5). 골밀도는수술전모 Percent (%) of inhibition of cathepsin K activity 1 5 Control OST 477 Fig. 1. Inhibition of human cathepsin K activity by OST-477. Table 1. Body weight and whole body BMD before starting treatments and at the end of treatments during the preliminary experiment (n = 5 in each group) Group Weight (g) BMD (g/cm 2 ) Baseline After 4 wk P value Baseline After 4 wk P value SHAM 18.6 ± ± ±.1.46 ±.1.1 OVX 18.4 ± ±.8 Ref.43 ±.1.44 ±.1 Ref CTKi 18.4 ± ±.5 NS.42 ±.1.44 ±.1.88 ZA ± ± 1.3 NS.42 ±.1.45 ±.1.13 ZA ± ±.7 NS.42 ±.1.46 ±. <.1 ZA1 PTH ± ± 1. NS.42 ±..46 ±.1 <.1 ZA1 PTH ± ±.5 NS.42 ±.1.47 ±.1 <.1 ZA2 PTH ± ±.8 NS.43 ±.1.49 ±. <.1 ZA2 PTH ± ±.3 NS.42 ±.1.5 ±.1 <.1 P value vs. OVX control at the end of treatments by analysis of variance with post-hoc analysis. SHAM, sham-operated mice; OVX, ovariectomized mice; CTKi, ovariectomized mice orally administered with OST mg/kg twice a daily; ZA1 and ZA2, ovariectomized mice intraperitoneally injected with zoledronic acid 1, 2 µg/kg once; ZA1 PTH1 and ZA1 PTH2, ovariectomized mice intraperitoneally injected with zoledronic acid 1 µg/kg once and subcutaneously injected with teriparatide 1, 2 µg/kg daily; ZA2 PTH1 and ZA2 PTH2, ovariectomized mice intraperitoneally injected with zoledronic acid 2 µg/kg once and subcutaneously injected with teriparatide 1, 2 µg/kg daily. BMD, bone mineral density; CTKi, cathepsin K inhibitor; NS, not significant; OVX, ovariectomized; PTH, parathyroid hormone; ZA, zoledronic acid.

4 36 Lee SH, et al. Change (%) of BMD Body weight (g) % (.1 to 9.7) SHAM OVX ZA CTKi PTH ZA PTH CTKi PTH 4.4% (-1.2 to 1.1) 2.6% (-3.1 to 8.2) 1.8% (-3.8 to 7.3) ZA1 SHAM OVX CTKi ZA1 ZA2 PTH1 4.8% (-.9 to 1.4) 2.4% (-3.2 to 8.1) ZA1 PTH2 4 8 Study days (wk) Fig. 3. Body weight before starting treatments and at the end of treatments during the main experiment (n = 8 in each group). P <.5. P <.1 vs. OVX control group. SHAM, sham-operated mice; OVX, ovariectomized mice; ZA, ovariectomized mice intraperitoneally injected with zoledronic acid 1 μg/ kg once; CTKi, ovariectomized mice orally administered with OST mg/ kg twice a day; PTH, ovariectomized mice subcutaneously injected with teriparatide 1 μg/kg daily; ZA PTH, ovariectomized mice intraperitoneally injected with zoledronic acid 1 μg/kg once and subcutaneously injected with teriparatide 1 μg/kg daily; CTKi PTH; ovariectomized mice orally administered with OST mg/kg twice a day and subcutaneously injected with teriparatide 1 μg/kg daily. BMD, bone mineral density; CTKi, cathepsin K inhibitor; OVX, ovariectomized; PTH, parathyroid hormone; ZA, zoledronic acid. ZA2 PTH1 ZA2 PTH2 Fig. 2. Change of whole body bone mineral density (BMD) during the preliminary experiment. P <.5 vs. CTKi group. SHAM, sham-operated mice; OVX, ovariectomized mice; CTKi, ovariectomized mice orally administered with OST mg/kg twice a day; ZA1 and ZA2, ovariectomized mice intraperitoneally injected with zoledronic acid 1, 2 μg/kg once; ZA1 PTH1 and ZA1 PTH2, ovariectomized mice intraperitoneally injected with zoledronic acid 1 μg/kg once and subcutaneously injected with teriparatide 1, 2 μg/kg daily; ZA2 PTH1 and ZA2 PTH2, ovariectomized mice intraperitoneally injected with zoledronic acid 2 μg/kg once and subcutaneously injected with teriparatide 1, 2 μg/kg daily. CTKi, cathepsin K inhibitor; OVX, ovariectomized; PTH, parathyroid hormone; ZA, zoledronic acid. 든군에서유의한차이가없었으나 (Fig. 4), 치료 4 주후에는 OVX 대 조군에비해 SHAM 군 (P =.1), PTH 군 (P =.1), ZA PTH 군 (P =.1), CTKi PTH 군 (P <.1) 에서유의하게증가하였다 (Fig. 4). 치료 8 주후에는 OVX 대조군에비해 SHAM 군 (P <.1), ZA 군 (P =.48), CTKi 군 (P =.27), PTH 군 (P =.18), ZA PTH 군 (P <.1), CTKi PTH 군 (P <.1) 에서유의하게증가하였다 (Fig. 4). PTH 군과 ZA PTH 군, CTKi PTH 군간의골밀도차이는 치료 4 주경에유의하지않았으나, 연구종료시점에서는 CTKi PTH 군에서.3 g/cm 2 (95% CI,.1 to.5) 로 ZA PTH 군의.1 g/cm 2 (95% CI, -.1 to.3) 에비해 PTH 군과유의한골밀도차 이를보였다 (P =.1) (Fig. 4). 골밀도의변화는치료 4 주후에 OVX 대조군에비해 SHAM 군 (P <.1), ZA 군 (P =.13), CTKi 군 (P =.11), PTH 군 (P <.1), ZA PTH 군 (P <.1), CTKi PTH 군 (P <.1) 에서유의하게증가하였다 (Fig. 5). 치료 8 주후에는 OVX 대조군에비해 SHAM 군 (P <.1), ZA 군 (P =.1), CTKi 군 (P <.1), PTH 군 (P =.1), ZA PTH 군 (P <.1), CTKi PTH 군 (P <.1) 에서유의하게증가하였다 (Fig. 5). ZA 군과 ZA PTH 군 간의골밀도변화의차이는치료 4 주경에 5.1% (95% CI, -1. to 1.) 로증가하는경향이보였으나 (P =.56), 치료 8 주후에는 3.3% (95% Whole body BMD (g/cm 2 ) SHAM OVX ZA CTKi PTH ZA PTH CTKi PTH NS NS NS 4 8 Study days (wk) Fig. 4. Whole body bone mineral density (BMD) before starting treatments and at the end of treatments during the main experiment (n = 8 in each group). P <.5 vs. OVX control group. P <.5 vs. PTH group. SHAM, sham-operated mice; OVX, ovariectomized mice; ZA, ovariectomized mice intraperitoneally injected with zoledronic acid 1 μg/kg once; CTKi, ovariectomized mice orally administered with OST mg/kg twice a day; PTH, ovariectomized mice subcutaneously injected with teriparatide 1 μg/kg daily; ZA PTH, ovariectomized mice intraperitoneally injected with zoledronic acid 1 μg/kg once and subcutaneously injected with teriparatide 1 μg/kg daily; CTKi PTH; ovariectomized mice orally administered with OST mg/kg twice a day and subcutaneously injected with teriparatide 1 μg/kg daily. CTKi, cathepsin K inhibitor; NS, not significant; OVX, ovariectomized; PTH, parathyroid hormone; ZA, zoledronic acid.

5 Effects of Combination Therapy of Cathepsin K Inhibitor and PTH on BMD Change 37 Change (%) of whole body BMD SHAM OVX ZA CTKi PTH ZA PTH CTKi PTH CI, -2.1 to 8.7) 로유의한증가는없었다. PTH 군과 ZA PTH 군, CTKi PTH 군간의골밀도변화의차이는치료 4 주경에유의하지않았으 나, 치료종료후에는 PTH 군에비해 ZA PTH 군에서 3.4% (95% CI, -1.5 to 8.3) 로유의한증가는없었으나 CTKi PTH 군에서는 7.3% (95% CI, 2.5 to 12.2) 로유의하게증가하였다 (P =.1) (Fig. 5). 고찰 본연구에서비스포스포네이트를 PTH 와병용시에 PTH 단독요 법에비해유의한골양의증가는관찰할수없었는데이는사람을 대상으로하였던다른연구결과들과일치하였다 [5,6]. 반면에 CTKi 를 PTH 와병용시에는흥미롭게도단독요법에비해골양이유의 하게증가되는것을확인하였다. 2.5 (-2.2 to 7.2).6 (-4.1 to 5.3) 4 8 Study days (wk) 7.3 (2.5 to 12.2) 3.4 (-1.5 to 8.3) Fig. 5. Change of whole body bone mineral density (BMD) before starting treatments and at the end of treatments during the main experiment (n = 8 in each group). P <.5 vs. OVX control group. P <.5 vs. PTH group. SHAM, shamoperated mice; OVX, ovariectomized mice; ZA, ovariectomized mice intraperitoneally injected with zoledronic acid 1 μg/kg once; CTKi, ovariectomized mice orally administered with OST mg/kg twice a day; PTH, ovariectomized mice subcutaneously injected with teriparatide 1 μg/kg daily; ZA PTH, ovariectomized mice intraperitoneally injected with zoledronic acid 1 ug/kg once and subcutaneously injected with teriparatide 1 ug/kg daily; CTKi PTH; ovariectomized mice orally administered with OST mg/ kg twice a day and subcutaneously injected with teriparatide 1 μg/kg daily. CTKi, cathepsin K inhibitor; OVX, ovariectomized; PTH, parathyroid hormone; ZA, zoledronic acid. CTKi 와비스포스포네이트를 PTH 와병용할때 PTH 의골형성작 용에대한두약제간의차이는골흡수억제효과의차이보다는 파골세포수에대한효과의차이때문이라고추정된다. 비스포스포 네이트를 PTH 와병용시에 PTH 의골형성작용을감소시키는현상 을설명하는기전으로골재형성과정중에골흡수와골형성이순 차적으로일어나는짝짓기현상의억제가제시되고있다 [7]. 최근에 는짝짓기조절인자들이전통적으로중요하다고알려져왔던골흡수단계과정보다는파골세포자체에서분비되기때문에, 짝짓기현상이파골세포수와밀접한관계가있다는근거들이제시되고있다 [7,22-24]. 이런관점에서 PTH와비스포스포네이트병용요법에의한결과는비스포스포네이트가파골세포의세포자멸사를증가시켜파골세포수를감소시키기때문에 [25,26], 파골세포에서나오는짝짓기조절인자들도감소하여 PTH에의한골형성이감소된것이라추정할수있다. 반면에, 1) CTK가결핍되어있는동물모델이나 [14], 2) CTK의효과가유전적으로감소된 pycnodysostosis 환자의일부 [24], 3) CTKi를동물에게처치한경우 [13,16] 들에서보이는것처럼 CTK가억제될때골흡수는억제되지만비스포스포네이트와는달리파골세포의수에는영향을끼치지않으며골형성효과에는영향을끼치지않는다고보고되었다. 이러한결과들은 CTKi를 PTH와병용시에 PTH에의한골형성효과가유지될가능성이있음을시사한다. 기대했던대로본연구의결과에서 CTKi를 PTH와병용시에비스포스포네이트와는달리 PTH 단독요법에비해유의한골양의증가를보여이러한가설을추정할수있었다. 또한본연구가진행되는동안 PTH와비스포스포네이트인알렌드로네이트 (alendronate, ALN) 혹은 CTKi인 KK1-3-1 병용요법에대한연구가발표되었다 [27]. 골조직형태계측분석과골형성표지자결과상 PTH 사용과무관하게 ALN은파골세포수와골형성작용을감소시키나, CTKi는파골세포수와골형성작용를감소시키지않았다. 또한 PTH와병용시에 CTKi는 ALN과는달리 PTH의골형성작용을증가시켰다. 이러한결과들은본연구의가설과결과에일치하였다. 추가적으로, 비스포스포네이트에비해골흡수억제정도가약한랄록시펜은 PTH와병용시에골양증가에대한상승효과를보였기때문에 [28], 골흡수억제정도가 PTH의골형성작용에영향을끼칠수있다는가능성을배제하기위해 OST-477과유사한골흡수억제정도를보이는비스포스포네이트의용량을확인후실험을진행하였다. 골흡수억제정도가 CTKi와유사한용량을쓴비스포스포네이트에서 PTH에의한골형성이역시감소되어, 골흡수억제정도보다는파골세포에대한영향이더중요함을확인할수있었다. 현재쓰이고있는골다공증치료제중가장널리사용되는골흡수억제제인비스포스포네이트는골흡수표지자를 8% 까지감소시킬정도로강력한골흡수억제작용이있지만골밀도의급격한증가가치료시작초기에만관찰되고, 3년이지난이후에는연 1% 미만의증가가있어오랜기간사용해도골밀도의증가가제한되어있다 [29,3]. 또한장기간사용은비정상적인대퇴골전자하부골절 [31], 골절치유지연 [32], 턱뼈괴사 [33] 등이야기될수있다고보고되고있다. 골형성촉진제인간헐적 PTH 주사요법은 21개월동안투여시요추골밀도를 9.7% 까지증가시켰으나 [34], 효과와안전성을위해 18-24개월간의투여만이허용되고있다 [4]. 따라서, 단일약제로서는골다공증환자에서단기간에골밀도를증가시키는것이어

6 38 Lee SH, et al. 렵기때문에골다공증치료제병용요법의필요성이대두되고있다. 본연구의결과에서보이는것처럼 CTKi는비스포스포네이트와는달리짝짓기현상을극복할수있는 decoupler 의가능성을가진약제로 PTH와병용시골흡수는억제하면서도골형성은촉진할수있어부작용은줄이면서골양을단시간에증가시킬수있으리라기대된다. 본논문작성중에사람에게서 ZA (5 mg 1회정주 ) 와 PTH (2 μg/ kg 매일피하투여 ) 의병용요법을 1년간시행한결과가발표되었다. 결과를살펴보면요추골밀도는병용요법군에서 7.5% 로 PTH 단독투여군의 7.% 나 ZA 단독투여군의 4.4% 에비해증가하였지만그정도가미미하였고, 대퇴전체골밀도는병용요법군에서 2.3% 로 PTH 단독투여군의 1.1% 나 ZA 단독투여군의 2.2% 에비해증가하였지만통계적으로유의하지않아본실험의결과와유사하였다 [35]. 본연구의제한점으로는골조직형태계측실험을실시하거나생화학적골표지자를측정하지못한것을지적할수있다. 결론적으로, 본생체실험을통해 PTH와병용시에 CTKi는비스포스포네이트와는달리짝짓기현상을극복하여골양을단기적으로유의하게증가시킬수있는것을확인이되었다. 향후다른동물모델을이용한실험이나임상연구를통해이에대한추가연구가필요할것으로사료된다. 요약배경 : 우리는카텝신 K 억제제와부갑상선호르몬 (1-34) 의병용요법이골흡수와골형성간의짝짓기현상을극복하여단기간에골양을유의하게증가시킨다고가정하였다. 방법 : 예비실험에서골양에대해카텝신 K 억제제인 OST-477 과유사한골밀도변화를보이는졸레드론산농도를선택하였다. 암컷생쥐에난소절제술 (OVX 군 ) 혹은가짜수술 (SHAM군) 을시행하였다. 8주동안카텝신 K 억제제 (CTKi군), 졸레드론산 (ZA군), 부갑상선호르몬 (1-34) (PTH군) 를투여하거나졸레드론산과부갑상선호르몬 (1-34) (ZA PTH군 ) 을병용투여하거나, 카텝신 K 억제제와부갑상선호르몬 (1-34) (CTKi PTH군 ) 을병용투여하였다. 전체골밀도를수술전, 처치후 4주, 8주뒤에측정하였다. 결과 : 예비실험에서는졸레드론산 1 μg/kg을투여시카텝신 K 억제제와유사한골밀도의변화를보였다. 골밀도는치료 8주후에 OVX 대조군에비해 SHAM군, ZA군, CTKi군, PTH군, ZA PTH군, CTKi PTH군에서유의하게증가하였다. 연구종료후골밀도는 CTKi PTH군에서 ZA PTH군과는달리 PTH군보다유의하게증가하였다. 골밀도의변화는치료 8주후에 OVX 대조군에비해 SHAM 군과 ZA군, CTKi군, PTH군, ZA PTH군, CTKi PTH군에서유의하게증가하였다. 치료종료후에골밀도의변화는 CTKi PTH군에서 ZA PTH군과는달리 PTH군보다유의하게증가하였다. 결론 : 카텝신 K 억제제는부갑상선호르몬과병용시부갑상선호 르몬의골형성효과를증가시켰다. 따라서, 카텝신 K 억제제와부갑 상선호르몬의병용요법은짝짓기현상을극복하여단기간에유의 하게골양을증가시킬수있는새로운치료전략이될수있음을시 사한다. 참고문헌 1. NIH Consensus Development Panel on Osteoporosis Prevention, Diagnosis, and Therapy: Osteoporosis prevention, diagnosis, and therapy. JAMA 285: , Recker R, Lappe J, Davies KM, Heaney R: Bone remodeling increases substantially in the years after menopause and remains increased in older osteoporosis patients. J Bone Miner Res 19: , Seeman E, Delmas PD: Bone quality-the material and structural basis of bone strength and fragility. N Engl J Med 354: , Canalis E, Giustina A, Bilezikian JP: Mechanisms of anabolic therapies for osteoporosis. N Engl J Med 357:95-916, Black DM, Greenspan SL, Ensrud KE, Palermo L, McGowan JA, Lang TF, Garnero P, Bouxsein ML, Bilezikian JP, Rosen CJ; PaTH Study Investigators: The effects of parathyroid hormone and alendronate alone or in combination in postmenopausal osteoporosis. N Engl J Med 349: , Finkelstein JS, Hayes A, Hunzelman JL, Wyland JJ, Lee H, Neer RM: The effects of parathyroid hormone, alendronate, or both in men with osteoporosis. N Engl J Med 349: , Karsdal MA, Martin TJ, Bollerslev J, Christiansen C, Henriksen K: Are nonresorbing osteoclasts sources of bone anabolic activity? J Bone Miner Res 22: , Nishi Y, Atley L, Eyre DE, Edelson JG, Superti-Furga A, Yasuda T, Desnick RJ, Gelb BD: Determination of bone markers in pycnodysostosis: effects of cathepsin K deficiency on bone matrix degradation. J Bone Miner Res 14: , Lark MW, Stroup GB, James IE, Dodds RA, Hwang SM, Blake SM, Lechowska BA, Hoffman SJ, Smith BR, Kapadia R, Liang X, Erhard K, Ru Y, Dong X, Marquis RW, Veber D, Gowen M: A potent small molecule, nonpeptide inhibitor of cathepsin K (SB 33175) prevents bone matrix resorption in the ovariectomized rat. Bone 3: , Saftig P, Hunziker E, Wehmeyer O, Jones S, Boyde A, Rommerskirch W, Moritz JD, Schu P, von Figura K: Impaired osteoclastic bone resorption leads to osteopetrosis in cathepsin-k-deficient mice. Proc Natl Acad Sci U S A 95: , Bone HG, McClung MR, Roux C, Recker RR, Eisman JA, Verbruggen N, Hustad CM, DaSilva C, Santora AC, Ince BA: Odanacatib, a cathepsin-k inhibitor for osteoporosis: a two-year study in postmenopausal women with low bone density. J Bone Miner Res 25: , Eisman JA, Bone HG, Hosking DJ, McClung MR, Reid IR, Rizzoli R, Resch H, Verbruggen N, Hustad CM, DaSilva C, Petrovic R, Santora AC, Ince BA, Lombardi A: Odanacatib in the treatment of postmenopausal women with low bone mineral density: three-year continued therapy and resolution of effect. J Bone Miner Res 26: , Kumar S, Dare L, Vasko-Moser JA, James IE, Blake SM, Rickard DJ,

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