Quarterly report pursuant to Section 13 or 15(d)

Commitments and Contingencies - Narrative (Details)

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Commitments and Contingencies - Narrative (Details)
3 Months Ended
Mar. 22, 2018
USD ($)
ft²
Dec. 04, 2017
USD ($)
Jan. 09, 2017
USD ($)
May 02, 2016
USD ($)
Mar. 31, 2018
USD ($)
employee
Mar. 31, 2017
USD ($)
Commitments and Contingencies [Line Items]            
Payments to HPI over three-year period       $ 750,000.00    
Buy-out option payment to HPI       $ 1,000,000.0    
HPI out-licensing agreement term       3 years    
Sponsored laboratory study agreement expense         $ 1,237,000 $ 683,000
Employee agreements, special termination benefits, number of employees | employee         4  
Employee agreements, termination benefits provided to key employees, aggregate amount         $ 1,000,000  
MD Anderson            
Commitments and Contingencies [Line Items]            
License costs         200,000 100,000
MD Anderson            
Commitments and Contingencies [Line Items]            
Payments for research and development agreement   $ 346,687 $ 302,500   236,687  
Payments for research and development agreement, next twelve months   $ 110,000        
Sponsored laboratory study agreement expense         291,687 33,000
Houston Pharmaceuticals, Inc.            
Commitments and Contingencies [Line Items]            
License costs         75,000 $ 75,000
Lease Agreement For Corporate Office Space | IPX Memorial Drive Investors, LLC            
Commitments and Contingencies [Line Items]            
Leased office space (in square feet) | ft² 2,333          
Term of operating lease (in months) 66 months          
Operating lease, renewal term (in years) 5 years          
Operating lease, monthly rent expense $ 4,300          
Operating lease, rent expense, annual increase in rent (as a percent) 3.00%          
Maximum            
Commitments and Contingencies [Line Items]            
Payments for royalties         600,000  
Maximum | MD Anderson            
Commitments and Contingencies [Line Items]            
License agreement, annual license fee         100,000  
Maximum | MD Anderson | Commencement of Phase II and Phase III Clinical Trials            
Commitments and Contingencies [Line Items]            
Milestone payments liabilities         500,000  
Maximum | MD Anderson | Submission Of NDA And Receipt Of First Marketing Approval For Sale Of A Licensed Product            
Commitments and Contingencies [Line Items]            
Milestone payments liabilities         $ 600,000