Summary of Significant Accounting Policies (Tables)
 12 Months Ended
Dec. 31, 2017
Accounting Policies [Abstract]  
Summary of Estimated Useful Lives of Property and Equipment

Depreciation is computed using the straight-line method over the estimated useful lives of the respective assets as follows:

 

 

 

Useful life

Office equipment

 

3 years

Electronic equipment

 

3 years

Vehicle

 

4 years

Laboratory equipment

 

5 years

Manufacturing equipment

 

10 years

Leasehold improvements

 

lesser of useful life or lease term

 
Liabilities Measured at Fair Value on Recurring Basis

Liabilities measured at fair value on a recurring basis as of December 31, 2016 are summarized below:

 

 

 

Level 1

 

 

Level 2

 

 

Level 3

 

 

 

$

 

 

$

 

 

$

 

Warrant liabilities

 

 

—

 

 

 

—

 

 

 

3,900,000

 

 
Binomial Model Assumptions to Estimate Fair Value of Warrant Liabilities

The Group used the binomial model to estimate the fair value of warrant liabilities using the following assumptions:

 

 

 

December 31, 2016

 

Risk-free rate of return

 

 

2.9

%

Vesting date

 

April 1, 2016

 

Maturity date

 

December 31, 2021

 

Estimated volatility rate

 

 

70

%

Exercise price

 

 

2.16

 

Fair value of underlying preferred shares

 

 

9.84

 

 
Suppliers Accounted for 10% or More of Research and Development Expenses

The following suppliers accounted for 10% or more of research and development expenses for the years ended December 31, 2015, 2016 and 2017:

 

 

 

Year ended December 31,

 

 

 

2015

 

 

2016

 

 

2017

 

 

 

$

 

 

$

 

 

$

 

A

 

 

5,703,000

 

 

*

 

 

*

 

B

 

*

 

 

 

14,625,500

 

 

*

 

C

 

*

 

 

*

 

 

 

7,651,617

 

D

 

*

 

 

*

 

 

 

7,104,015