Safety Study of XT-150 in Participants With ALS

This is a Phase 1, open-label, multi-center safety study of XT-150 in adult participants with Amyotrophic Lateral Sclerosis (ALS).

Participants providing informed consent and meeting all study eligibility criteria will be enrolled in the study and will receive a single injection of XT-150 at the Baseline visit. Follow-up visits will occur over 180 days (6 months) after the injection.

8 participants (4 participants per dose level) will be enrolled sequentially in up to 2 ascending, single dose cohorts: Cohort 1: 1.5 mg XT-150 Cohort 2: 4.5 mg XT-150

The main questions this study is aiming to answer are:

* What adverse events are reported during this study? An adverse event is any "side effect" that participants have during a study. Adverse events may or may not be caused by XT-150. The study doctors will check participants' ALS and general health throughout the trial.
* Does XT-150 have any effects on participants' physical examination findings, vital signs, or laboratory values?

In addition to evaluating the safety of XT-150, this study will also collect samples to provide information on the following:

* The levels of XT-150 in your body
* The effect of XT-150 on cytokines including interleukin (IL)-10
* The effect of XT-150 on relevant ALS biomarkers such as Neurofilament Light (NfL)

In addition, ALS functional score, breathing capacity and strength will be collected over the course of the study.

Eligibility Criteria:
Key Inclusion Criteria:

* Adults between 18 and 80 years of age
* Male or female, if of childbearing potential or sexually active, strict contraception required
* Have ALS diagnosed by a doctor (specifically, sporadic or familial ALS diagnosed as clinically probable, lab-supported probable or definite ALS defined by the El Escorial criteria)
* Have had symptoms of ALS (muscle weakness) within 36 months of starting this study
* Have the ability to slowly exhale a volume of air at least 60% of what is expected for the participant's sex, height and age
* Have not received treatment for ALS or are currently on a stable dose of an approved treatment for ALS. Patients currently receiving Tofersen are not eligible.
* Able to receive the study injection intrathecally, determined by the study doctor
* Able to undergo the study procedures and adhere to the study visit schedule at the time of study entry, with an estimated life expectancy of 6 months or greater

Key Exclusion Criteria:

* Have an implanted shunt to drain cerebrospinal fluid (CSF) or an implanted CNS catheter
* Have an implanted of diaphragm pacing system
* Tracheostomy
* History or current diagnosis of cardiac conditions or ECG abnormalities indicating significant risk of safety for participants in the study
* History or current diagnosis of respiratory conditions such as COPD
* History or current diagnosis of cancer, chemical meningitis, HIV, Hep B, Hep C, uncontrolled diabetes
* Presence of an autoimmune condition (for example, rheumatoid arthritis or lupus) requiring treatment or immunodeficiency
* Clinical or laboratory evidence of hepatic or renal disease/injury.
* Taking any prohibited medications
* Women who are pregnant or nursing
* Use of any investigational drugs or devices within 30 days or 5 half-lives of the study agent (whichever is longer). Exception: Observational, non-interventional clinical studies are allowed in the opinion of the study doctor.
* Any other condition that the study doctor feels could compromise the participant's safety, ability to communicate with the study staff, or the quality of the data