Branched chain amino acids in the treatment of polymyositis and dermatomyositis: a phase II/III, multi-centre, randomized controlled trial

Abstract

Introduction

PM/DM are autoimmune diseases that affect skeletal muscle. Patients suffer from muscle weakness, decreased muscle endurance and restriction of activities of daily life. Glucocorticoids (GCs) and immunosuppressants are generally effective as treatments although muscle function frequently remains impaired even after muscle enzyme normalization. A cross-sectional study in the Japanese nationwide registration system database revealed that about half of patients under treatment suffered from muscle weakness while a quarter had elevation of serum myogenic enzymes [1]. Several observational studies showed that perceived disabilities and impacts on quality of life were of long duration in myositis patients [2–4]. Residual impairment of muscle functions is a problem for patients with PM/DM worldwide.

One of the major causes of residual muscle weakness is muscle fibre atrophy resulting from chronic inflammation and glucocorticoid use [5]. Atrophy of muscle fibers arises from the disbalance of anabolism and catabolism of the muscle protein [6]. The ubiquitin–proteasomal pathway is responsible for the catabolic processes of muscle proteins [7]. This pathway is stimulated via the transcriptional activation of the muscle-specific ubiquitin-ligases, atrogin-1 and MuRF1. These are upregulated by proinflammatory cytokines such as TNF-α and IL-1 through NF-κB and by GCs through glucocorticoid receptors (GR) [8–11]. GCs also mediate anti-anabolic actions by inhibiting the transport of amino acids into the muscle and repressing mammalian target of rapamycin (mTOR) signalling [11, 12]. Once the muscle becomes atrophic, it is difficult and time-consuming to restore muscle volume. So far, the only way to do so is by rehabilitation, and recently, evidence-based recommendations for exercise in the treatment of idiopathic inflammatory myopathies were proposed [13].

Branched-chain amino acids (BCAAs) have protective effects against muscle atrophy. Administration of BCAAs was reported to abrogate muscle atrophy and attenuate the increase of atrogin-1 and MuRF1 in hindlimb suspension-induced muscle atrophy in rats [14]. BCAA supplementation ameliorated muscle atrophy and activated mTOR signalling in angiotensin II-induced muscle atrophy in mice [15]. The same effects were observed in dexamethasone-induced muscle atrophy in rats, the model of steroid myopathy [16]. In a murine model of PM, BCAA administration prevented the reduction of muscle weight and muscle weakness of C protein-induced myositis (CIM) (unpublished data). Izumi et al. reported that administration of BCAAs alleviated muscle weakness in two patients with PM who had been treated with GCs and immunosuppressants [17]. Yoshikawa et al. demonstrated that BCAA supplementation improved skeletal muscle strength and function in patients with rheumatic disorders treated with GCs, which suggested their efficacy in preventing steroid myopathy [18].

BCAAs are indicated for the treatment of hypoalbuminemia in decompensated liver cirrhosis in Japan. They are suitable for combination with immunosuppressive treatments because of their safety profiles and the absence of immunosuppressive effects. Thus, BCAAs have the potential to become the first medication targeting the impairment of muscle functions in PM/DM patients.

The BTOUGH (‘BCAA for Treatment of Underpowered muscles during Glucocorticoid Healing of PM and DM’) study was aimed at investigating the efficacy and safety of BCAAs for alleviating muscle weakness in patients with PM/DM. The study used a double-blind, randomized, placebo-controlled design. The manual muscle test (MMT) was utilized for assessing the primary endpoint while the functional index (FI) was applied for the assessment of the endurance of selected muscles. The response to treatment was evaluated with a core set of measures proposed by the International Myositis Assessment and Clinical Studies Group (IMACS) [19].

Methods

Trial design

The BTOUGH study was a phase II/III trial. The trial was carried out in three phases: the investigational phase, the transitional phase and an extension phase (Fig. 1). The investigational phase was from the start of drug administration (week 0) to week 12. Patients were randomly allocated to receive TK-98 (drug name of BCAAs) or placebo at week 0 in a 1:1 ratio using a centralized random assignment system. Randomization was stratified by disease (PM or DM), mean MMT score at screening (<7, <8 or <9.5) and institution. Patients, investigators and site staff were masked to the allocations. The primary endpoint was evaluated at week 12. The transitional phase was from week 12–16. The data acquired in the investigational phase were fixed and indications for extended administration were judged at this time. Patients whose average MMT score at week 12 was <9.5 were enrolled in an open label extension phase from week 16–28 to assess the safety of long-term TK-98 use and whether the efficacy observed in the investigational phase was retained over a longer duration. This trial was carried out from April 2015 to April 2017 at 23 Japanese institutions. The Institutional Review Board of each hospital, listed in Supplementary Data S1 (available at Rheumatology online), approved this study. Written informed consent was obtained from each participant. The study was conducted in accordance with the declaration of Helsinki, Good Clinical Practice and applicable regulatory requirements.

Fig. 1

Schematic diagram of the design of the BTOUGH study

Participants were randomized to receive TK-98 or placebo. The primary endpoint was evaluated with data from week 12. Patients with an average MMT score <9.5 at week 12 were enrolled in an open label extension study and all received TK-98. BTOUGH: the ‘BCAA for Treatment of Underpowered muscles during Glucocorticoid Healing of PM and DM’ study.

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Patients

Treatment-naïve adults aged 20–75 years with a diagnosis of definite or probable PM/DM according to the criteria of Bohan and Peter [20] were eligible. Patients had active muscle involvement with average MMT scores >6 and <9.5 with elevated serum CK or aldolase levels above the upper limit of normal. Treatment with high doses of GCs equivalent to or >0.75 mg/kg/day or 60 mg/day of prednisolone was indicated for them. Exclusion criteria is shown in Supplementary Data S2, available at Rheumatology online. MMT was performed to evaluate the strength of the following muscles (bilaterally, except for the neck): neck flexor, neck extensor, deltoid, biceps brachii, triceps brachii, brachioradialis, iliopsoas, gluteus maximus, quadriceps femoris and hamstrings. Evaluation was scored by the definition of Kendall and McCreary [21]. The initial dose of GCs was maintained for at least 2 weeks and dose adjustment was allowed within 20% of the initial dose at week 2 that was maintained until week 4. After week 4, the dose of GCs was reduced by 10% every 2 weeks. Concomitant use of immunosuppressants listed in Supplementary Data S3 (available at Rheumatology online) was allowed from week 2 at the attending physicians’ discretion.

Patients were hospitalized for at least 4 weeks from day 0. Rehabilitation was allowed when the CK value had any decrease over two consecutive measurements after 4 weeks. However, minimum extent of rehabilitation to maintain their ranges of motion or daily activities was allowed from the start of treatment. The criteria for discharge were set as follows: (i) when the dose of prednisolone had been reduced to ≤0.5 mg/kg/day, (ii) when the CK value had decreased by 10% or more from the previous value over two consecutive measurements, (iii) when the CK value had any decrease over three consecutive measurements, or (iv) when the CK value had improved to within the normal range over two consecutive measurements. For patients who met any of these criteria, the investigators then reviewed muscle function to decide whether the patient could be discharged. Participants were required to record their walk counts and exercise in their diaries every day.

We aimed to recruit 60 patients to detect a statistically significant difference assuming 0.67 points of difference in MMT score between groups (s.d. = 0.92) with 80% power.

Intervention

One package of TK-98 (4.15 g) contained l-isoleucine 952 mg, l-leucine 1904 mg and l-valine 1144 mg (molar ratio is 1:2:1.35). Six packages of TK-98 or placebo were orally administered daily in three divided doses at the start of glucocorticoid treatment.

Outcomes

The primary endpoint was the change of MMT score at 12 weeks. Secondary endpoints were clinical response evaluated with the myositis disease activity core set and the change of FI, which evaluates dynamic repetitive muscle functions. FI was evaluated for the following movements: shoulder flexion, head lift and hip flexion, bilaterally except for head lift.

Statistical analysis

Pearson’s Chi-squared tests and t-tests was used to assess difference in baseline categorical and continuous characteristics, respectively. MMT and FI scores were analysed using a restricted maximum likelihood based mixed-effect models for repeated-measures approach in combination with the Newton–Raphson algorithm. Analyses included fixed categorical treatment, time, treatment-time interaction and PM/DM, as well as the fixed continuous baseline score. An unstructured covariance structure was used to model the within-patient errors. Significance tests will be based on least-squares means (LS mean) using a two-sided alpha of 0.05. Fisher’s exact test was used to assess difference in response criteria and safety. Missing data were not imputed.

Results

Baseline characteristics

Forty-nine patients were screened, of whom 47 were accepted for randomization (Fig. 2). Although we aimed to recruit 60 patients, we failed to achieve this before the support by the Japan Agency for Medical Research and Development ended. Twenty-four patients were allocated to the TK-98 group, 23 to the placebo group. There were no significant differences between the two groups in age at diagnosis, disease duration, gender and disease classification (Table 1). All patients except one, who was diagnosed with PM by the criteria of Bohan and Peter, underwent muscle biopsy and were confirmed to have histological changes. The baseline MMT scores were equivalent [mean (s.d.) 7.97 (0.92) in the TK-98 group and 7.84 (0.86) in the placebo group], and the average MMT score was 6 points for 20%, 7 points for 30% and 8 or more for the remaining 50%. About half had interstitial lung disease. Most patients received concomitant immunosuppressants.

Fig. 2

Flow diagram of participants in the BTOUGH study

The data of all patients who were allocated were analysed. BTOUGH: the ‘BCAA for Treatment of Underpowered muscles during Glucocorticoid Healing of PM and DM’ study.

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Primary outcome

Changes of average MMT scores were similar between the TK-98 and placebo groups (Fig. 3A) and there was no significant difference in the change of MMT scores between week 0 and 12 [mean (s.e.m.) 0.70 (0.19) in the TK-98 group vs 0.69 (0.18) in the placebo group; P = 0.98]. Thirteen patients in the TK-98 group and 12 patients in the placebo group moved to an open label extension phase, all receiving TK-98. There was no difference between the two groups in the changes of the mean MMT scores from week 0–28, showing constant improvement (Fig. 3B). Changes of MMT scores in the subgroups of PM and DM were similar to the whole group (supplementary Fig. S1, available at Rheumatology online).

Fig. 3

Transitional changes of MMT scores

(A) Mean MMT scores from baseline to 12 weeks (n = 24 in the TK-98 group, 23 in the placebo group). The baseline MMT scores were the same [mean (s.d.) 7.97 (0.92) in the TK-98 group vs 7.84 (0.86) in the placebo group]. Changes of MMT scores at 12 weeks from baseline were [mean (s.e.m.)] 0.70 (0.19) and 0.69 (0.18), respectively (P = 0.98). (B) Mean MMT scores of patients who entered the open label extension phase from baseline to 28 weeks (n = 13 in the TK-98 group, 12 in the placebo group). Error bars represent s.d. MMT: manual muscle test.

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Secondary outcomes

Clinical response

Clinical responses at 12 weeks were evaluated based on the 2016 ACR/EULAR criteria [22]. Minimal, moderate and major improvement was achieved in 100%, 82.4% and 29.4% of the TK-98 group and 100%, 83.3% and 38.9% of the placebo group, with no differences between the two (supplementary Fig. S2A, available at Rheumatology online). The improvement scores of each core set measure at 12 weeks were similar between the two (supplementary Fig. S2B, available at Rheumatology online). The results were consistent when they were subdivided to PM and DM (supplementary Fig. S2C, available at Rheumatology online). Changes of total improvement score throughout the study were shown in the supplementary figure (supplementary Fig. S2D, available at Rheumatology online).

Dose of GCs

The total doses of GCs were calculated by summation of each prescribed dose converted to mg prednisolone per kg body weight equivalent from day 0 to week 12, because the amount of GCs would affect muscle strength. There was no difference between the two groups (supplementary Fig. S2E, available at Rheumatology online).

FI score

FI scores of the TK-98 group showed more improvement than the placebo group. The increase per unit of time of the mean FI scores of five motions was significantly greater in the TK-98 group than in the placebo group on the statistical assumption that FI scores improve linearly from baseline to week 12 (Fig. 4A). The changes of FI scores of bilateral shoulder flexions from week 0 to week 12 were greater in the TK-98 group than in the placebo group [27.9 (5.67) vs 12.8 (5.67) in the right shoulder flexion (P < 0.05), 27.0 (5.44) vs 13.4 (5.95) in the left shoulder (P < 0.05)] (Fig. 4A). There was no difference in the other movements.

Fig. 4

Transitional changes of FI scores

(A) Mean FI scores in the investigational phase (n = 24 in the TK-98 group, 23 in the placebo group). The improvement rate of the average score of all motions through the first 12 weeks was greater in the TK-98 group (*P < 0.05). The increase of FI scores of right and left shoulder flexions from baseline to week 12 was greater in the TK-98 group (**P < 0.05). (B) Mean FI scores of those who participated in the extension study (n = 13 in the TK-98 group, 12 in the placebo group). The improvements of shoulder flexions from baseline at each time point marked with a dagger (†) were greater in the TK-98 group (^†P < 0.05). Solid circles with a line represent the TK-98 group and open squares with a broken line represent the placebo group. Error bars represent s.e.m. FI: functional index.

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FI scores of those who participated in the extension study showed similar tendencies to improve as those in the investigational phase (Fig. 4B). Because all participants received TK-98 from week 16, we could not compare the TK-98 group and the placebo group on the assumption of linear improvement from baseline to week 28. However, the changes of FI scores for bilateral shoulder flexions from baseline showed better improvement in the TK-98 group at several visits (Fig. 4B). Changes of FI scores of PM and DM were almost similar to the whole group (supplementary Figs S3 and S4, available at Rheumatology online).

Safety

Adverse events were observed in over 90% of patients in the investigational phase with no significant difference between the two groups, most being attributed to the use of high-dose GCs (Table 2). Five severe adverse events in four cases and three severe adverse events in two cases were reported in the TK-98 group and the placebo group, respectively. One patient who attempted suicide had a history of depression and commencing high dose GCs together with tetracyclic antidepressants seemed to trigger the event. However, the local Institutional Review Board judged that unknown mutual interactions between TK-98 and GCs or antidepressants could not be excluded.

Discussion

We evaluated the effects of adding BCAA treatment on muscle function of patients with PM/DM during initial treatment with conventional GCs and immunosuppressants. The observed improvement of MMT scores in the first 12 weeks did not indicate any differences between the BCAA group and the placebo group. A similar degree of improvement was also observed in the extension phase where all participants whose mean MMT score at week 12 was <9.5 received BCAAs. Although the primary endpoint was not achieved and official approval could not be gained, this trial is unique in that the effect of BCAAs has been evaluated for the first time for the treatment of muscle weakness in PM/DM patients.

Nonetheless, improvement of the FI score was greater in the BCAA group. FI evaluates the ability to perform the indicated articular movement at the same tempo for 3 min and does not require maximum muscle contraction, thus reflecting muscle endurance [23]. Therefore, the FI score may be a better indicator of the muscle function required for the activities of daily life than is the MMT score. In fact, the FI score correlates well with patient-reported outcomes [24]. Also in the present trial, improvement of HAQ and patient visual analogue scale for muscle strength showed a significant correlation with improvement of FI scores, but not with improved MMT scores. The superior improvement of the FI score is a clinically meaningful outcome for PM/DM patients.

Why FI was able to demonstrate an effect of BCAAs on muscle functions but MMT could not is unclear, but several hypotheses can be proposed. First, FI may simply be more sensitive than MMT. Comparison of FI2 and MMT in myositis patients showed that the former was evidently abnormal and variable in patients with normal or almost normal MMT scores [25]. When the functional impairment of muscle is mild, small differences in the function of each muscle may not be apparent by MMT but become evident by repetitive dynamic loading. Second, FI may depend more on muscle fibre type or mitochondrial function rather than muscle volume. Muscle fibers are classified into two major groups: type I and type II fibers. Type I fibers are slow-twitch, oxidative and have large mitochondria, making them suitable for aerobic exercise, whereas type II fibers are fast-twitch, mainly glycolytic and have few small mitochondria, suitable for anaerobic exercise [26]. PM/DM patients in the chronic phase have a lower proportion of type I fibers than untreated patients or healthy controls [27]. Exercise could help to recover the proportion and cross-sectional area of type I fibers, accompanied by an improvement in the FI score [28]. However, in the mouse angiotensin II-induced muscle atrophy model, BCAA supplementation for 4 weeks ameliorated muscle atrophy with a greater effect on type II than type I fibers [15]. In another study using middle-aged mice, BCAA-enriched mixture supplementation for 3 months increased mitochondrial biogenesis in muscle, and restored fibre sizes accompanied by enhanced endurance capacity [29]. Moreover, in a human study, 8-h infusion of BCAAs enhanced the maximal mitochondrial ATP production rate in young adults [30]. Although the effect of long-term administration of BCAAs in humans has never been determined, the above observations indicate that BCAAs could act on mitochondria in muscle fibers and influence muscle endurance capacity. Third, it is known that BCAAs may be a direct energy source for skeletal muscle [31, 32]. BCAAs can be more efficient carbon sources of oxidation for energy production than glucose [33–35]. However, this would be a short-term effect. As the FI scores of the placebo group did not catch up with those of the TK-98 group in the extension phase where all participants received BCAAs, the improvement of FI scores observed in the present study presumably resulted from a long-term effect of BCAA treatment. At the same time, this indicates that an early intervention with BCAA is important for the restoration of muscle functions.

FI improvement was shown only in shoulder flexion. We have no explanation for this at present. There was no difference in changes of MMT scores of deltoid and biceps brachii like that for other muscles between the TK-98 group and the placebo group. In the past study of intensive resistance training in patients with chronic PM/DM, significant improvement of FI2 was observed only in shoulder flexion, although 10–15 voluntary repetition maximum improved in muscles of both upper and lower limbs [36]. These results may suggest that FI of shoulder flexion is easy to improve.

Our results indicate that MMT is an insufficient metric for the evaluation of muscle function. MMT and FI should both be utilized, at least in clinical trials. Evaluating muscle endurance besides MMT is important in patients with higher MMT scores. FI can quantitatively distinguish differences of muscle function that MMT cannot. However, FI requires much more time and patient cooperation. A truncated version of FI may resolve this problem [37].

In the present study, a dose of BCAA double that prescribed for patients with liver cirrhosis in Japan was administered. Its safety profile was acceptable. However, a suicide attempt was reported in one patient with a history of depression who was receiving antidepressants together with high-dose GCs, suggesting that caution is required when using BCAAs in such patients.

BCAAs can be obtained as an over-the-counter drug and used by those who are training their muscles. However, one dose of TK-98 used in this trial contained 7 g of BCAAs, i.e. 1.4- to 3.5-fold the dose of the over-the-counter drug. Absorption of amino acids is influenced by gut microbiota [38]. Combinations of BCAAs and probiotics may enhance absorption and the effects of BCAAs. In addition, the ratio of ingredients in BCAAs may have room for optimization for muscle protein synthesis because leucine is recognized as the key amino acid of the three [32, 33, 39]. Because sarcopenia associated with several different diseases is a major problem in an ageing society, modified drugs for treating muscle weakness and atrophy are expected to emerge.

There are a few limitations in this study. First, the criteria of Bohan and Peter were used. Thus, we did not discriminate immune-mediated necrotizing myopathy from PM. Nonetheless, we excluded cases suspected of IBM from clinical features. Second, we did not collect data on autoantibodies. Thus, together with the first limitation, diagnosis of PM/DM was entrusted to investigators at each site.

In conclusion, adding BCAAs to the treatment of PM/DM did not meet the primary endpoint, leaving the possibility that BCAAs may alleviate the impairment of muscle function in myositis patients. As data from humans are limited, we hope that revised trials will proceed with suitable primary endpoints including the evaluation of muscle endurance and with optimized drug formulations.

Acknowledgements

We thank Ryuji Koike, Michi Tanaka, Akito Takamura, Yoko Yoshihashi-Nakazato, Natsuka Umezawa, Hirokazu Sasaki, Mari Kamiya, Makoto Tomita and Haruko Hiraki for their assistance. We thank Yoshiaki Hanzawa, Eri Ishibashi, Asuka Hikichi, Kayoko Kajiwara and Aya Kato for their clerical support. We thank EA Pharma Co., Ltd for providing study drugs. We thank I’rom Group Co., Ltd and EPS Corporation for their cooperation.

Funding: This work was supported by Japan Agency for Medical Research and Development (AMED).

Disclosure statement: N.K. reports grants from Chugai, Union Chimique Belge (UCB), CSL Behring, Ayumi, Japan Blood Products Organization (JBPO) and Novartis, and honoraria for lectures from Eisai, AbbVie, Asahi-Kasei, Novartis, JBPO, Kissei, Ono and Mitsubishi-Tanabe. K.H. reports research funding from Astellas, Bayer, Chugai, Kyowa-Kirin and Ono, consulting fees from GlaxoSmithKlein (GSK), and honoraria for lectures from Astellas, Daiichi-Sankyo, GSK, Ono and Sanofi. T.A. reports grants from Astellas, Mitsubishi-Tanabe, Chugai, Daiichi-Sankyo, Pfizer, Teijin, Novartis, Eli-Lilly, Kyowa-Kirin, AbbVie, Nippon-Shinyaku, Taiho, Boehringer Ingelheim, Amgen and UCB, consulting fees from Pfizer, Novartis, AbbVie, AstraZeneca, Eli-Lilly and Ono, and honoraria for lectures from Takeda, Astellas, Mitsubishi-Tanabe, Chugai, Daiichi-Sankyo, Pfizer, Alexion, Teijin, Novartis, Eli-Lilly, Kyowa-Kirin, AbbVie, Boehringer Ingelheim, Amgen, UCB and AstraZeneca. T.M. reports grants from Asahi-Kasei, Astellas, Chugai, Eisai, Janssen, Pfizer and Mitsubishi-Tanabe, and honoraria for lectures from AbbVie, Asahi-Kasei, Astellas, Ayumi, Chugai, Daiichi-Sankyo, Eisai, Eli-Lilly, Mitsubishi-Tanabe, Ono, Pfizer, Takeda and UCB. T.Kanda reports honoraria for lectures from JBPO. Y.T. reports grants from Asahi-Kasei, AbbVie, Chugai, Mitsubishi-Tanabe, Eisai, Takeda, Corrona, Daiichi-Sankyo, Kowa and Behringer-Ingelheim, and honoraria for lectures from Gilead, Abbvie, Behringer-Ingelheim, Eli-Lilly, Mitsubishi-Tanabe, Chugai, Amgen, YL Biologics, Eisai, Astellas, Bristol-Myers Squibb (BMS) and AstraZeneca. A.K. reports competitive funding from AMED and The Japanese Ministry of Health, Labour and Welfare (JMHLW), joint research with Boehringer Ingelheim, and honoraria for lectures from Boehringer Ingelheim. H.K. reports research grants from AbbVie, Asahi-Kasei, Chugai, Eisai and Mitsubishi-Tanabe, consultation fees from AbbVie and Novartis, and honoraria for lectures from AbbVie, Asahi-Kasei, Astellas, Boehringer-Ingelheim, BMS, Chugai, Eisai, Elli-Lilly, Janssen, Kyowa-Kirin, Mitsubishi-Tanabe, Novartis, Pfizer, Sanofi and UCB, Advisory Board of AbbVie, Asahi-Kasei, Astellas, BMS, Elli-Lilly, Janssen and Pfizer, and Monitoring Board of Sanofi and UCB.

Data availability statement

The data underlying this article will be shared on reasonable request to the corresponding author.

Supplementary data

Supplementary data are available at Rheumatology online.

References