Trial Outcomes & Findings for A Study of TAK-341 in Treatment of Multiple System Atrophy (NCT NCT05526391)

Participants participated across investigative sites in the United States, Austria, Denmark, France, Germany, Italy, Japan, Portugal, Spain, and the United Kingdom between 16 November 2022 and 28 July 2025.

A total of 158 participants with possible or probable multiple system atrophy (MSA), received multiple intravenous (IV) infusions of either TAK-341 or placebo, every 4 weeks (Q4W) over 52 weeks. The study comprised of a screening period of 6 weeks, a 52-week treatment period, and a follow-up visit approximately 90 days after the final infusion.

A Study of TAK-341 in Treatment of Multiple System Atrophy

UMSARS Part I (historical review) is a 12-item scale that was adapted from the Unified Parkinson's Disease Rating Scale (UPDRS) and is used to assess activities related to motor disability and autonomic dysfunction. In this study, the UMSARS was modified to exclude the sexual function item. Thus, total 11 items were assessed. Each item was initially scored on a scale from 0 (normal) to 4 (severe); ratings of normal (0) and mild (1) were then combined and recorded as 0, making minimum score 0 and maximum score 3. The investigator rated the average functional situation for the past 2 weeks according to findings from the participant and caregiver interview and indicated the score that best fit with the participant's status. The total score is a sum of scores from all domains and range from 0 to 33. Higher scores indicate worse impairment.

The 11- item UMSARS includes 11 items from Part I and II to assess both motor and autonomic disability. UMSARS Part I (historical review) is used to assess activities related to motor disability and autonomic dysfunction. UMSARS Part II (motor examination) is used to measure the functional impairment and specific parkinsonian or cerebellar features. Each item was scored on a scale from 0 (normal) to 4 (severe); total score ranges from 0 to 44, higher scores indicated worse impairment.

UMSARS total scale consists of all items from UMSARS Parts I and II. UMSARS Part I (historical review): 12-item scale used to assess activities related to motor disability and autonomic dysfunction. Each item is scored from 0 (normal) to 4 (severe). UMSARS Part II (motor examination): 14-item scale used to measure the functional impairment (for example speech, rapid alternating movements of the hands, finger taps, leg agility) of selected complex movements, and specific parkinsonian (tremor at rest) or cerebellar (ocular motor dysfunction, heel-shin test) features. The worst affected limb was assessed, and each item was scored from 0 (normal) to 4 (severe). UMSARS Part I and Part II total score is the sum of UMSARS Part I and Part II and ranges from 0 to 104. A higher score indicates worse impairment.

UMSARS Part I (historical review) is a 12-item scale that was adapted from the UPDRS. In this study, the UMSARS was modified to exclude the sexual function item. The UMSARS is used to assess activities related to motor disability and autonomic dysfunction. Each item was scored on a scale from 0 (normal) to 4 (severe). UMSARS Part I 11-item total score is the total score of UMSARS Part I, excluding the sexual function item, and without collapse of ratings of scale items. The UMSARS Part I 11-item total score ranges from 0 to 44, and higher scores indicate worse impairment.

UMSARS Part II (motor examination): 14-item scale used to measure the functional impairment (e.g., speech, rapid alternating movements of the hands, finger taps, leg agility) of selected complex movements, and specific parkinsonian (tremor at rest) or cerebellar (ocular motor dysfunction, heel-shin test) features. the worst affected limb was assessed, and each item was scored from 0 (normal) to 4 (severe). The UMSARS Part II total score ranges from 0 to 56, and higher scores indicate worse impairment.

The CGI-S is used to assess the clinician's impression of the participant's clinical condition. The clinician rates the current severity of the participant's illness on a 7-point scale ranging from 1 (normal, not at all ill) to 7 (most extremely ill). The rating was based on observed and reported symptoms, behaviour, and function and reflected the severity level at the time of the assessment. A higher score indicates worse impairment.

The SCOPA-AUT is a participant-reported outcome that assesses autonomic function. Autonomic function is a critical symptom domain for MSA. The scale was completed by participants and consisted of 25 items assessing the following domains: gastrointestinal (7 items), urinary (6 items), cardiovascular (3 items), thermoregulatory (4 items), pupillomotor (1 item), and sexual (2 items for men and 2 items for women). The score for each item ranged from 0 (never experiencing the symptom) to 3 (often experiencing the symptom). The total composite score including all domains was reported. The score range was 0 (no symptoms) to 69 (highest burden of symptoms). A higher score indicates worse impairment.

OS was estimated with Kaplan-Meier survival estimates, along with 95% confidence interval. A cox proportional hazards model was fitted to model the survival probability with treatment as the predictor. The participants with missing value were censored. The probabilities of survival at Week 52 for participants were estimated and reported.

α-Synucleinopathies are diseases characterized by abnormal accumulation of aggregated αSYN. In participants with MSA, αSYN is seen to accumulate primarily in oligodendrocytes, forming glial cytoplasmic inclusions. A negative change from Baseline indicates an improvement.

Cmax is the maximum observed serum concentration for TAK-341.

Tmax is the time of first occurrence of maximum observed concentration for TAK-341.

AUCτ is the area under the serum concentration-time curve during a dosing interval.

Lumbar puncture was performed for CSF on Day 1, Day 85 and Day 365, predose.

An adverse event (AE) is defined as any untoward medical occurrence in a participant administered a pharmaceutical product; it does not necessarily have to have a causal relationship with this treatment. An AE can therefore be any unfavorable and unintended sign (e.g., a clinically significant abnormal laboratory finding), symptom, or disease temporally associated with the use of a drug, whether or not it is considered related to the drug. A TEAE is defined as an adverse event that occurs after administration of the first dose of study treatment and up through 90 days after the last dose of study treatment.