‣ A patient is eligible when all inclusion criteria and none of the exclusion criteria are fullfilled in the ANeED study:

• Male or female.

• Age ≥ 50 and ≤ 85 years of age.

• Confirmed diagnosis of Dementia with Lewy Bodies (DLB) or Mild Cognitive Impairment in DLB (DLB-MCI).

• MMSE score\>=15

• Able and willing to provide informed consent prior to any study related assessments and procedures at screening visit 1.

• Capable of complying with all study procedures.

• Willing to provide blood samples for genetic analyses of APOE and GBA.

• Willing and able to self-administer or administer by a caregiver oral ambroxol medication, from day 1 to study end (at 60 mg TID (day 1-7), 120 mg TID (day 8- 14), 315 BID (day 15-21), 315 mg TID (day 22-28) and 420 mg TID (day 29-550)).

• Able to travel to the participating study site.

⁃ A female participant is eligible to participate if she is of:

‣ Non-childbearing potential defined as pre-menopausal females with a documented tubal ligation or hysterectomy; or postmenopausal defined as 12 consecutive months of spontaneous amenorrhea, at least 6 weeks post-surgical bilateral oophorectomy (with or without hysterectomy) or post tubal ligation. In questionable cases, menopausal status will be confirmed by demonstrating levels of follicle stimulating hormone (FSH) 25.8 - 134.8 IU/L and oestradiol \< 201 pmol/l at entry.

‣ Women of child-bearing potential must use accepted contraceptive methods (listed below), and must have a negative serum at screening visit 1 and urine pregnancy tests at subsequent visits if applicable. An additional pregnancy test will be performed, and results obtained, prior to administration of the first dose of ambroxol.