This is a phase 1/2a randomised, placebo controlled, double-blind study investigating the safety, tolerability, pharmacokinetics, and pharmacodynamics of ALE1 on healthy adult subjects and adult patients with Hypophosphatasia (HPP).

Key Inclusion Criteria Part 1:

1. Participants are overtly healthy as determined by a medical evaluation
2. No concurrent medical conditions or significant medical history, in the opinion of the investigator.

Key Inclusion Criteria Part 2:

1. Documented ALPL gene variant

Key Exclusion Criteria Part 1:

1. History of conditions affecting bone or mineral metabolism

Key Exclusion Criteria Part 2:

1. Previous treatment with an enzyme replacement therapy (ERT) or any advanced therapeutic agent (e.g., gene therapy) for the treatment of hypophosphatasia (HPP) or any treatment for osteoporotic diseases
2. Previous exposure to any medication or investigational agent potentially affecting bone structure, muscle volume, muscle strength, or muscle or nerve function
3. Diagnosis of hyperparathyroidism
4. Diagnosis of hypoparathyroidism, unless secondary to HPP
5. New fracture within 12 weeks before first dosing