Breakthrough cancer pain (BTcP) is a common problem in patients with cancer. This is a phase IIa dose-response and safety study of inhaled fentanyl aerosol (25µg/dose) in Chinese patients with breakthrough cancer pain.

Consenting patients who met inclusion and exclusion criteria were allowed to enter the study. The medication for background pain during screening were maintained until the end of the study. Each patient would be treated and observed for 6 episodes of targeted BTcP. Patients were randomly assigned to 1 of the 6 prespecified dose sequences which were established by a computer-generated schedule of active drug and placebo in a 4:2 ratio. All patients and personnel involved with the study (including investigators and investigation site personnel) were blinded to the medication codes.

Inclusion Criteria:

1. Age of 18 years or above
2. Subjects must be diagnosed with cancer.
3. Subjects must experience persistent pain associated with cancer, and the pain score assessed by NRS should be <4 within 1week before screening.
4. In the past 7 days, the subject must experience an average of 1 to 4 episodes of breakthrough cancer pain per day,The breakthrough cancer pain score should be ≥4 assessed by NRS
5. ECOG status of 0 to 2.
6. Subjects must consent to take adequate contraception during the study and 1 months after the study. Women of childbearing potential must show negative in the pregnancy test before dosing.
7. The subject must be able to understand the requirements of the study and provide a written informed consent.

Exclusion Criteria:

1. History or suspected allergies to fentanyl.
2. HGB < 80 g/L, NEUT ≤1.0 × l09/L, PLT ≤50 × l09/L；ALT and AST higher than 3 times of ULN;total bilirubin and Cr higher than 1.5 times of ULN;PaO2 <95%;FEV1/FVC<70% and FEV1 accounted for less than 80% of the predicted value.
3. Any uncontrolled disease (e.g., severe mental, neurological, infectious, cardiovascular, respiratory and other systemic diseases).
4. Tumor infiltration to central nervous system.
5. Subjects are not able to slef evaluate pain intensity using NRS
6. Receive surgery in past 3 weeks
7. Treatment with any form of radiotherapy winth 1week prior to study entry that could alter pain or response to pain medication.
8. Taking monoamine oxidase inhibitors(MAOIs), CYP3A4 inhibitors or inducers within 14 days of the screening
9. Participated in other clinical trials in past 1months.
10. Pregnancy and breast-feeding women, women of childbearing age ready to conceive, and pregnancy test positive.
11. Other conditions that may affect the informed consent, compliance with the protocol, study results and safety of the subject.