Part 1 will evaluate the safety, tolerability and PK of single doses of three dose levels of NTX-1175 drug substance administered by dry powder inhaler (NOC-110) compared to a single dose reference nebulizer (NOC-100) treatment in healthy participants.

Part 2 will evaluate the safety, tolerability and PK of multiple doses of NTX-1175 drug substance administered by dry powder inhaler (NOC-110) to participants with refractory chronic cough. Part 2 will also evaluate the treatment effect of multiple doses of one dose level of NTX-1175 drug substance administered by dry powder inhaler (NOC-110).

Part 1 is a randomized, double-blinded 3 period crossover and 1 period parallel study of single dose administration of NOC-110 via dry powder inhaler, preceded by a reference period of NOC-100 administered via nebulizer. A total of 12 healthy participants will be enrolled to ensure that 9 participants complete this part of study.

Part 2 is a randomized, double-blinded, placebo-controlled, multiple-dose, parallel design study in patients with refractory chronic cough. A total of 12 participants will be enrolled to ensure that 8 participants complete this part of study.

Inclusion Criteria:

Participants must meet all of the following criteria to be eligible for participation in the study:

1. Male or female participants between the ages of 18 to 65 years, inclusive, at the time of screening (Part 1) and between the ages of 18 to 85 years, inclusive, at the time of screening (Part 2).
2. Has had rCC diagnosis for ≥ 12 months (Part 2) prior to screening.
3. Awake-cough frequency of ≥20 per hour (average) at Screening (Part 2).
4. Score of ≥40 mm on the Cough Severity Visual Analog Scale (VAS) at Screening (Part 2).
5. Chest radiograph or CT thorax within the last 60 months not demonstrating any abnormality considered to be significantly contributing to the rCC. (Part 2)
6. Body mass index (BMI) ≥19.0 and ≤32.0 kg/m2, inclusive, at Screening.
7. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) <2 x upper limit of normal (ULN); alkaline phosphatase (ALP) and bilirubin ≤1.5 x ULN (isolated bilirubin >1.5 x ULN is acceptable if bilirubin is fractionated and direct bilirubin <35%).
8. Creatinine clearance ≥50 mL/min.
9. Must be fully SARS-CoV-2 vaccinated.
10. Must be SARS-CoV-2 negative via rapid antigen testing or polymerase chain reaction (PCR) test at Screening and PCR at Check-in Day -1.
11. In the Investigator's opinion, has no clinically significant disease and/or clinically significant abnormal laboratory values as determined by the Investigator based on medical history, physical examination, or laboratory evaluations conducted at the screening visit or on admission to the clinical research unit.

Exclusion Criteria:

Participants who meet any one of the following criteria will be deemed ineligible for participation in the study:

1. Is found to have positive test for SARS-CoV-2 at Screening or Check-in Day -1, whether or not this was accompanied by the clinical symptoms of COVID-19.

2. Current smoker or individuals who have given up smoking within the past 6 months prior to screening, or those with >20 pack-year smoking history (Part 2)

3. Current diagnosis of chronic obstructive pulmonary disease (COPD), bronchiectasis, unexplained pulmonary fibrosis, or asthma (Part 2).

4. History or presence of alcohol or drug use disorder, per Diagnostic and Statistical Manual of Mental Disorders, fifth edition (DSM-5), within the past 2 years prior to screening.

5. Current opiate/opioid use in the past 7 days prior to screening, or medical history of opiate/opioid use disorder.

6. Unable to refrain from the use of:

   1. Gabapentin, pregabalin, and/or amitryptline or other tricyclics within 4 weeks prior to screening and throughout the study (Part 2)
   2. Chronic, systemic corticosteroid use within 4 weeks prior to screening and throughout the study (Part 2).
   3. Inhalers including long-acting and short acting beta 2-agonists (LABA and SABA), and inhaled corticosteroids (ICS) within 8 weeks prior to screening and throughout the study.
   4. Lidocaine or related compounds of any form within 14 days prior to screening and throughout the study (Part 2).
   5. Medication or remedies to aid sleeping 14 days prior to screening and throughout the study (Part 2).
   6. Angiotensin-converting enzyme (ACE)-inhibitor within 12 weeks prior to screening and throughout the study (Part 2).
   7. Antitussives 7 days prior to screening and throughout the study (Part 2).
   8. Speech and language therapy for rCC within 4 weeks prior to screening and throughout the study (Part 2).
   9. Food and beverages containing alcohol for 24 hours prior to screening (Part 2).

7. History or presence of cardiac dysfunction including arrhythmia, bundle branch block; Wolff Parkinson White syndrome, recent thromboembolic event, prolonged PR (≥220 msec), QRS (≥120 msec), QTcF interval (≥450 msec [males] or ≥470 msec [females]) or has ECG findings deemed abnormal with clinical significance by the Investigator or designee at Screening.

8. Positive results at Screening for HIV, HBsAg, or HCV (participants successfully treated for HCV may be permitted at the discretion of the Investigator).

9. Supine blood pressure is less than 90/40 mmHg or greater than 140/90 mmHg (Part 1), or greater than 160/95 mmHg (Part 2) at Screening. Vital signs may be repeated twice.

10. Supine heart rate is lower than 40 beats per minute (bpm) or higher than 99 bpm at Screening. Vital signs may be repeated twice.

11. History of asthma or COPD (Part 1).

12. Forced expiratory volume in 1 second/ forced vital capacity (FEV1/FVC) < lower limit of normal (LLN) per Global Lung Health Initiative normative dataset at Screening.

13. Had symptoms of any significant acute illness, including symptoms of COVID-19 within 30 days before the start of the study (time of first dose), as determined by the Investigator.

A computerized randomization scheme for Part 1 and Part 2 will be created by a blinded study statistician and it shall be considered blinded per the following: The randomization is available only to the unblinded Clinic pharmacy staff who are preparing the study drug and who will not be involved in any other aspect of the study including administration of the study drug. The randomization scheme will not be made available to the Sponsor, study participants, or members of the staff responsible for the monitoring and evaluation of safety assessments.