Here is the design of a clinical trial:

Official Title: Sintilimab Plus Bevacizumab in Patients With Recurrent/Persistent Ovarian Clear Cell Carcinoma

Included conditions:
- Ovarian Clear Cell Carcinoma

Study Armgroups:
- {'label': 'Combination Arm', 'type': 'EXPERIMENTAL', 'description': 'Sintilimab 200mg iv., q3w, up to 2 years; Bevacizumab 15mg/kg iv., q3w, up to 22 cycles. Treatment is given until confirmed progression, death, unacceptable toxicity, or any other protocol-specified criterion for withdrawal, whichever occurs first.', 'interventionNames': ['Drug: Sintilimab', 'Drug: Bevacizumab Biosimilar IBI305']}

Interventions:
- {'type': 'DRUG', 'name': 'Sintilimab', 'description': 'Sintilimab 200mg iv. q3w, up to 2 years.', 'armGroupLabels': ['Combination Arm'], 'otherNames': ['IBI308']}
- {'type': 'DRUG', 'name': 'Bevacizumab Biosimilar IBI305', 'description': 'Bevacizumab 15mg/kg iv. q3w, up to 22 cycles', 'armGroupLabels': ['Combination Arm'], 'otherNames': ['IBI305']}

Primary Outcomes:
- {'measure': 'Objective response rate (ORR)', 'description': 'ORR is defined as the proportion of patients with complete response(CR) and partial response(PR) assessed by the investigator in accordance with the RECIST 1.1 criteria.', 'timeFrame': 'Up to 3 years'}

Please estimate the sample size based on the assumption: 
Using the Simon two-stage design with a significance level (α) of 0.05 and power (β) of 0.2. Considering a dropout rate of 10%.
Sample size
        The sample size was estimated based on the primary endpoint of ORR. A retrospective study of recurrent or refractory OCCC reported a 6%â8%âresponse rate for second-line treatment.8 Therefore, the null hypothesis is postulated of an ORR of 8% (P0), while 23% or more in the experimental in this study (P1). Using the Simon two-stage (Optimum) design with unilateral Î±=0.05âand Î²=0.2, totally 38 patients will be enrolled in this trial. In the first stage of accrual, 17 patients were enrolled. The response rate will be determined, if the total number of patients responding to sintilimab and bevacizumab is less than or equal to one patient, then the trial should terminate early and declare no worth of further investigation for the combination therapy. On the contrary, 17 patients will be recruited in the second stage, with a total of 34 patients. If the total number of patients achieving complete or PR is less than or equal to five cases, then the null hypothesis is true, and the trial does not reach the effective endpoint. Otherwise, it is determined that the combination regimen is effective and worthy of further large-scale clinical trials. Considering a dropout rate of 10%, a total of 38 patients will be included in this study.