In this study, we demonstrated that GV1001 might have beneficial effects on the cognition and activities of daily living in patients with moderate-to-severe AD already receiving donepezil.
Since the approval of memantine, no drugs have been approved for AD. Although the FDA approval of aducanumab is awaited , certainly, there is a huge unmet medical need. Searching for additional pathomechanisms of AD and developing drugs with multifunctional effects are important. ROS resulting in oxidative stress, which is induced by aging, Aβ, and amyloid precursor protein, contributes to the pathogenesis of AD . ROS may be involved in Aβ fibrillization in AD, which makes it a vicious cycle . Neuroinflammation also plays a major role in the pathogenesis of AD. Although the inflammatory response may have beneficial effects by removing Aβ and tau, sustained inflammatory responses are detrimental . At the early stage of Aβ pathology, Aβ is generally surrounded by the neuroprotective phenotype of microglia . As the disease progresses, the microglia switch to a more neurotoxic phenotype [27, 28]. In our previous study, GV1001 restricted the production of ROS, which was increased by Aβ oligomer . Moreover, GV1001 decreased death and inflammation-related proteins, which were increased by Aβ or oxidative stress [14, 15]. In addition to its anti-oxidant and anti-inflammatory effects, GV1001 showed some other beneficial effects, such as anti-aging and mitochondria-stabilizing effects against Aβ toxicity and other stressors [14,15,16]. GV1001 effectively entered the brain through the brain-blood barrier, which was confirmed in the MRI and Prussian blue staining studies detecting subcutaneously injected GV1001 labeled with ferrocenecarboxylic acid (Fe) (Additional file 2, Figure S1). Hence, we hypothesized that GV1001 might be helpful in the treatment of patients with AD.
This clinical trial showed that GV1001, especially at a dose of 1.12 mg, effectively reduced the change in SIB scores compared with the placebo treatment, suggesting that GV1001 might have beneficial effects in patients with moderate-to-severe AD. We assessed the change in the SIB score from baseline to week 24 as a primary endpoint because SIB is suitable for evaluating patients with moderate-to-severe AD as it overcomes the floor effects of patients with more advanced disease . In our control group, the SIB score significantly decreased from baseline to week 24; however, this decrease was consistent with that reported in previously published clinical trials [30, 31]. In a previous study including patients with moderate-to-severe AD, the decrease in the SIB score was > 10 in the control group 28 weeks after initiation of the trial . In another study, the SIB score was 6.6 in the control group after 24 weeks of applying a rivastigmine patch (4.6 mg/24 h) , although this decrease was significantly higher than the approximate SIB score of 2 at 24 weeks reported in several other studies [32, 33].
As the other primary endpoint, we assessed the safety of GV1001. There was no difference in the TEAEs between the three groups; additionally, no severe TEAEs were noted in the GV1001 groups, regardless of the dose (Table 3 and Tables S7 and S8 in Additional file 2), suggesting that the administration of GV1001 0.56 and 1.12 mg is as safe as the administration of normal saline. This finding will make it easier for us to perform subsequent clinical trials. The number of dropouts was not significantly different among the three groups (5 in group 1, 10 in group 2, and 7 in group 3, p = 0.356). Participants from a single center were excluded after the administration of the first study treatment, due to mandatory clinical data, including baseline clinical data and the results of neurological examination performed at the corresponding time points, were not uploaded to the central web-based system and the investigator of this center could not verify the source of these data (Fig. 2). The exclusion resulted in a slightly higher number of dropouts in group 2. Nevertheless, this exclusion occurred randomly as the allocation of participants from this center occurred randomly by the Interactive Web Response System and there was no significant difference in the baseline clinical characteristics among patients who dropped out.
Regarding the secondary endpoints, the pattern of the changes from the baseline in ADCS-ADL and CDR-SOB were similar to that of the primary endpoint; however, the change was not statistically significant (Table 2 and Fig. 3). The relatively small number of subjects might have restricted us from showing statistical significance. The NPI scores showed a statistically significant improvement at week 12 in the GV1001 1.12 mg group, even though the significance was not maintained at week 24 (Table 2). There were no significant differences in other secondary endpoints between the GV1001 groups and control group. The effect of GV1001 on the secondary endpoints needs to be confirmed in a larger clinical trial because our study was performed to investigate the feasibility of GV1001 for the treatment of moderate-to-severe AD, and the size of each group was small.
This study has merit in that significant benefit was observed for GV1001 at both weeks 12 and 24 with a relatively small number of patients with moderate-to-severe AD. The diverse neuroprotective effects of GV1001, such as its anti-inflammatory, anti-aging, antioxidant, and mitochondria-stabilizing effects, might reveal these results. However, further research is needed to show the association between these neuroprotective effects and biomarkers of AD. The incidence of dropout and AEs were comparable among the three groups.
The limitations of this study include the enrollment of a single ethnic population and short duration of follow-up. However, as we enrolled elderly and vulnerable (moderate-to-severe AD) patients, the concern about high attrition rates restrained us from planning a longer study period (≥ 12 months). For this reason, several previous randomized controlled trials involving moderate-to-severe AD observed participants for approximately 6 months [30, 34]. When we decided to enroll patients with moderate-to-severe AD, we considered our in vivo study results (unpublished data) showing that GV1001 significantly improved the neurobehavioral functions of old (from the age of 21 months until the endpoint) 3xTg-AD mice (B6:129-Psen1tm1Mpm Tg[APPSwe, tauP301L]1Lfa/Mmjax), which are comparable to patients with moderate-to-severe AD. As we enrolled patients with moderate-to-severe AD, a group receiving only GV1001 without donepezil was not evaluated in terms of ethical problems. Moreover, drugs other than donepezil (i.e., memantine) for the treatment of AD were prohibited because it would be difficult to show the effectiveness of the drug in the first human clinical with a small number. Additionally, we could not include pharmacokinetic (PK) data, as the detection level of GV1001 in the blood was extremely low to show a sufficient PK profile in humans. The peptides may rapidly degrade before their uptake by antigen-presenting cells . The doses of the investigational drug to be used in this study were determined by the process for deriving the maximum recommended starting dose for the first-in-human clinical trials of new molecular entities and preclinical experiments in an AD mouse model. Finally, biomarkers associated with AD were not investigated as a part of AD diagnosis because the diagnosis was based on DSM-IV and the 2011 recommendations from the National Institute on Aging-Alzheimer’s Association workgroups on diagnostic guidelines for Alzheimer’s disease, which did not recommend any biomarker studies for the diagnosis of moderate to severe AD . Moreover, this clinical trial had been planned before the 2018 National Institute on Aging-Alzheimer’s Association Research Framework was published , so we did not consider any biomarker studies in this trial. Nevertheless, this might have biased the diagnosis of AD in a few patients. Therefore, to overcome this bias, additional biomarkers, including neurodegeneration biomarker (hippocampal volume or cortical thickness), Aβ positivity, and apolipoprotein E genotyping, should be considered in future larger clinical trials. Evaluating the level of neurofilament light or tau in blood or cerebrospinal fluid can be also helpful in proving the biological effect of GV1001.