This protocol will seek to enroll up to 60 immunocompromised subjects diagnosed with parainfluenza infection.

All subjects will have additional PK and Immunogenicity blood samples collected.

The study will investigate the safety, tolerability, clinical and virologic effect of DAS1814 for the treatment of PIV infections in up to 60 immunocompromised patients with no other treatment options.

Eligible immunocompromised patients positively diagnosed with PIV infection will receive DAS181 by DPI or Nebulized formulation.

DPI: 10 mg DAS181 will be administered for seven (7) consecutive days for up to a total cumulative dose of 70mg.

Nebulized: DAS181 F02 formulation in solution will be administered for seven (7) consecutive days for up to a total cumulative dose of 28.9 mg.

Assessment of viral shedding and viral resistance testing will be performed on collected viral load samples. Blood samples will be obtained to evaluate safety at each scheduled visit.

Routine safety monitoring (including Adverse Event (AE) reporting, clinical laboratory tests, vital signs, electrocardiogram (ECG) and )2 levels) will be conducted in all subjects. A final safety assessment will occur at Day 28 (+/- 2 days) after enrollment/first dose of study drug. Survival, diary cards, and quality of life will be collected at Day 60 and 90. PK will be collected at each visit on all subjects from baseline/visit 2 to visit 11/Day 28. Immunogenicity samples will be collected at selected time points in all subjects.

Inclusion Criteria:

1. Age ≥12 years

2. Able to provide informed consent or child assent with parental consent

3. Immunocompromised, as defined by one of the following:

   • Allogeneic hematopoietic cell transplantation (HCT)
   • Lung or lung-heart transplantation
   • Patients treated with chemotherapy for hematologic malignancies or autologous HCT

4. Confirmed Parainfluenza virus by nasopharyngeal swab or tracheal aspirate for one of the following:

   • Respiratory virus panel
   • DFA
   • Qualitative/quantitative RT-PCR test for parainfluenza virus performed at the local laboratory (a confirmatory PCR test will be done at the central lab but is not required to start the patient on study).

5. Female subjects of child-bearing potential who are capable of conception must be:

   post-menopausal (one year or greater without menses), surgically incapable of childbearing, or practicing two effective methods of birth control. Acceptable methods include intrauterine device, spermicide, barrier, male partner surgical sterilization and hormonal contraception. A female subject must agree to practice two acceptable methods of birth control during the 28 day study period. Abstinence is not an acceptable method of contraception. All reproductive female subjects must have a negative serum pregnancy test during the screening visit.

6. Male subjects must agree to use medically accepted form of contraception during the 28 day study period.

Exclusion Criteria:

1. Psychiatric or cognitive illness or recreational drug/alcohol use that, in the opinion of the principal investigator, would affect patient safety and/or compliance.
2. Any significant finding in the patient's medical history or physical examination that, in the opinion of the investigator, would affect patient safety, ability to use the dry powder inhaler or compliance with the dosing schedule.
3. Subjects currently treated with oral, aerosolized or IV ribavirin
4. Subjects taking any investigational drug used to research or treat PIV