A Study of TAK-071 in People With Parkinson Disease

Key Inclusion Criteria: 1. Is an outpatient of any sex aged between 40 and ≤ 85 years, inclusive, at the time of consent. 2. Has a diagnosis of PD according to Movement Disorders Society (MDS) clinical diagnostic criteria for PD. Participants with DLB (i.e., dementia diagnosed before onset of motor symptoms or up to 1 year after onset of motor symptoms) are also eligible, consistent with MDS clinical diagnostic criteria for PD. 3. Has Hoehn and Yahr stage ≥2 and \<4 at the screening visit. 4. Has elevated risk for falls as indicated by at least 1 fall in the last 12 months before the screening visit based on the Fall History Assessment where in the opinion of the investigator the falls were a consequence of PD and are at continued elevated risk of falls per investigator judgment. Investigator judgment on fall risk may be informed by information such as, but not limited to, history, physical examination and/or a score ≥2 on item 3.10 on Movement Disorders Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS) Part III. 5. Has evidence of cognitive impairment as indicated by a Montreal Cognitive Assessment (MoCA) score between 11 and 26, inclusive and additionally can complete the cognitive assessments at screening (as specified in the study manual). 6. Can walk without aid for 2 minutes while doing serial 3 subtraction (with site staff ensuring participant safety in case of falls). Participants who require aids for walking can be included as long as they can complete the walk test without aid. Inclusion For Healthy Participants: 1\. The participant is a healthy individual of either sex aged between 56 and 75 years, inclusive (for initial set of participant in the sentinel cohort) at the time of consent. Older participants may be enrolled after analysis of data from participants aged 56 to 75 years, inclusive. NOTE: Other protocol defined Inclusion/Exclusion criteria may apply Key Exclusion Criteria: 1. Has orthostatic hypotension at screening, as defined as a decline in systolic blood pressure greater than 20 mm Hg or a decrease of 10 mm Hg in diastolic blood pressure on standing measured within 1 minute after being supine for at least 5 minutes. 2. Has dyskinesia of sufficient severity to interfere with digital gait assessments during visits (as defined by Movement Disorders Society - Unified Parkinson's Disease Rating Scale \[MDS-UPDRS\] section 4.1 "Time spent with dyskinesias" and/or section 4.2 "Functional Impact of Dyskinesias" scores greater than \[\>\] 2), or in the opinion of the investigator the participant's dyskinesia is likely to interfere with the digital gait assessments. 3. Has significant risk factors for seizures (a history of seizures as an adult, a history of brain injury, or other risk factors deemed relevant by the investigator). 4. Is considered by the investigator to be at imminent risk of suicide or injury to self, others, or property, or the participant has attempted suicide within the past year before screening. Participants who have positive answers on item number 4 or 5 on the Columbia-Suicide Severity Rating Scale (C-SSRS) (based on the past year) before randomization are excluded. 5. Is unwilling or unable to discontinue taking cholinesterase inhibitors and/or moderate or strong cytochrome P-450 3A4 inhibitors or inducers at least 30 days before randomization. Exclusion For Healthy Participants: 1. Participants has body mass index (BMI) less than 18 or greater than 40. 2. Has significant risk factors for seizures (a history of seizures as an adult, a history of brain injury, or other risk factors deemed relevant by the investigator). 3. The participant is unwilling or unable to discontinue taking cholinesterase inhibitors and/or moderate or strong CYP 3A4 inhibitors or inducers at least 30 days before randomization. 4. The participant is taking warfarin. NOTE: Other protocol defined Inclusion/Exclusion criteria may apply