Min J-H, et al. • Oral Ursodeoxycholic Acid Therapy in Amyotrophic Lateral Sclerosis domized patients completed both parts of the study with missed visits, followed by lost to follow-up, being the most common drop-out reason. The patients, who had already severe disease at enrollment or became progressively more disabled during the study, tended to refuse to visit the clinic for outcome measures. These patients were also hard to keep contact with for consistent follow-up. Thus, it is likely that the broad inclusion criteria regard- ing disease severity, and the lack of adherence to visit schedule for outcome measures account for the large attrition rate. The second problem of this study is the way data were analyzed, i.e., ‘completers-only’ analysis. Since only the patients who com- pleted the planned treatment course were included for efficacy analysis, this does not conform to the intention-to-principle. We cannot rule out faster declines for patients after their dropout, and excluded cases can cause a bias, although baseline clinical features of patients completing the study and patients dropping- out the study were not different. However, we could not apply the intention-to-treat principle, since the attrition rate was too large for us to perform any valid imputation procedure for miss- ing data. Other limitations of this study are the short treatment period and limited number of datapoints to assess the rates of functional deterioration. Treatment period of 3 months might not be sufficient duration to capture a small effect. In addition, the outcome measures may not be reproducible to give accu- rate statistics with only two datapoints. Finally, it also should be pointed out that all the patients who were excluded due to their rapid progression rates (> 8 points/month) were those taking oral solubilized UDCA. An ethical concern about treatment with placebo was the main reason we adopted a cross-over design instead of conventional two parallel arm study (27). It was also expected that the cross- over design would be more efficient in detecting the same effect with a smaller sample size, since within-patient variability may be smaller than between-patient variability when the deteriora- tion rates of functional scales are used as endpoints (28, 29). However, there might be disadvantages to the cross-over trial as well, and some of these indeed caused difficulties for analysis and interpretation of our study. First, there may be a bias which is related to the unequal randomization for the first treatment period. It is likely that merely the sequence of treatment may explain the difference between treatments, although we adjust- ed the effects of sequence and period using ANCOVA to evalu- ate the effect of treatment itself. The other problem is a treatment- period interaction, so-called a carry-over effect. The wash-out period of 1 month may be insufficient to completely eliminate the effect of treatment given before. However, we could exclude the inflation of alpha-error resulting from the carry-over effect, because any persistence of the drug effect would have reduced the magnitude of difference during the second treatment period. It is worth emphasizing that UDCA can be effectively deliv- ered to the central nervous system (CSF) with oral administra- http://dx.doi.org/10.3346/jkms.2012.27.2.200 tion of solubilized UDCA in our study. A recent pilot study by Parry et al. also showed that UDCA was well absorbed after oral administration and crossed the blood-brain barrier in a dose- dependent manner in ALS patients (30). Eighteen patients were received UDCA in tablet formula at doses of 15, 30, and 50 mg/ kg of body weight per day and the concentration of UDCA in CSF ranged 43.1 to 281.7 nM/L after 4 weeks of treatment. These results suggest that oral UDCA is well delivered to CSF of ALS patients and the therapeutic effects deserve to be expected al- though it remains to be elucidated which formula or dose of UDCA is more tolerated, absorbed, delivered and effective in ALS patients. Although the mechanisms of cytoprotection of UDCA remain to be elusive, it does not seem to be limited to hepatic cells. UDCA modulates the apoptotic threshold in both hepatic and non-he- patic cells through the downregulation of p53 pathway (10, 11). Recently, a study using oral solubilized UDCA demonstrated that UDCA treatment can suppress cisplatin-induced p53 accu- mulation and apoptosis in mouse sensory neurons (19). It was also reported that this highly soluble and acid stable UDCA for- mula can scavenge the reactive oxygen species and prevent apop- tosis in Helicobacter pylori-induced gastritis (20). In line with these previous reports, we also found that the new UDCA for- mula improved the motor performance and survival of G93A SOD1 mutant transgenic mice (in preparation). Therefore, the therapeutic effect of UDCA may be ascribed to the successful delivery of UDCA to the central nervous system and its multiple cytoprotective actions. Oral solubilized UDCA treatment seems to be tolerable in ALS patients, but regarding the efficacy we could not make any con- clusions due to several problems and limitations of this pilot study as discussed above. Still, the effect of UDCA deserves to be expected in ALS, due to its multiple neuroprotective mecha- nism. As we know, a phase II trial for the efficacy and tolerabili- ty of tauroursodeoxycholic acid, taurine conjugate of UDCA in ALS patients is also ongoing (NCT00877604) by Italian research- ers. Further large scale study with minimal attrition rate is war- ranted to confirm the efficacy and safety of oral solubilized UDCA for patients with ALS. ACKNOWLEDGMENTS The authors thank to Seo Hong Yoo and Dong Jin Yoo for the de- tection of oral solubilized UDCA in human CSF. REFERENCES 1. Mitchell JD, Borasio GD. Amyotrophic lateral sclerosis. Lancet 2007; 369: 2031-41. 2. Boillée S, Vande Velde C, Cleveland DW. ALS: a disease of motor neu- rons and their nonneuronal neighbors. Neuron 2006; 52: 39-59. http://jkms.org 205