Safety, Tolerability and Biomarker-based Efficacy of NPI-001 (AT-001) in Subjects With MCI or Alzheimer's Disease (AD)

The study aims to measure safety, tolerability and biomarker-based efficacy of NPI-001 (AT-001) in Subjects with MCI or Alzheimer's Disease (AD). In the study participants receive increasing dose of active treatment (250mg vs 500mg vs 750mg) or matched placebo in the form of tablets BID.

Inclusion Criteria: 1. Subject has provided informed consent for participation in trial. 2. Subject is male or female, aged 50 or older but younger than 85. 1. Female Subjects: * Of child-bearing potential in the age range of 50-60 years who are still menstruating, are willing to perform a pregnancy test at screening visit, V1 (Baseline) and at each subsequent visit and adhere to contraception requirements. * Of nonchildbearing Potential (WONCBP), women in the following categories are considered WONCBP: Premenopausal female permanently sterile due to one of the following (for the purpose of this study): Women who have documented hysterectomy, documented bilateral salpingectomy, documented bilateral oophorectomy * Postmenopausal female is defined as no menses for 12 months. If confirmation is needed, a high follicle stimulating hormone (FSH) level in the postmenopausal range will be used to confirm a postmenopausal state in women not using hormonal contraception or hormonal replacement therapy (HRT). Females on HRT and whose menopausal status is in doubt must discontinue HRT to allow confirmation of postmenopausal status before study enrollment. 2. Male subjects: * Male subjects with female partners of child-bearing potential who are willing or able to adhere to contraception requirements, or male subjects with documented infertility. 3. Subject has MCI or mild dementia due to Alzheimer´s disease according to Jack 2024 with a CDR of 0.5 or 1.0 receiving standard AD care (SOC) (65). 4. Subject has an MMSE score of \>21 \< 28 5. Subject is willing to have a baseline and follow up blood tests according to the schedule of assessments, for up to 12 months. 6. Subject has a pTau 217 value of \> 0.35 pg/ml 7. Subject is willing and able to undergo MRI, and amyloid PET scan evaluations of the brain, which fulfill the following requirements: 1. PET amyloid brain load \>32 centiloids 2. MRI \