| STOCK-BASED COMPENSATION | 
 
		
			NOTE 7 – STOCK-BASED COMPENSATION
		 
		
			The following table summarizes stock-based option compensation for the three and six months ended June 30, 2019 and 2018:
		 
		
			 
		 
		
			
				| 
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						For the three months ended June 30,  
				 | 
				
					 
						  
				 | 
				
					 
						For the six months ended June 30,  
				 | 
			 
			
				| 
					 
						  
				 | 
				
					 
						     
				 | 
				
					 
						2019 
				 | 
				
					 
						     
				 | 
				
					 
						2018 
				 | 
				
					 
						     
				 | 
				
					 
						2019 
				 | 
				
					 
						     
				 | 
				
					 
						2018 
				 | 
			 
			
				| 
					 
						Research and development 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				
					 
						 1,009,000 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				
					 
						 900,000 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				
					 
						 2,041,000 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				
					 
						 1,744,000 
				 | 
			 
			
				| 
					 
						General and administrative 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						 669,000 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						 1,773,000 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						 1,740,000 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						 2,829,000 
				 | 
			 
			
				| 
					 
						Stock-based compensation expense included in operating expense 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						 1,678,000 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						 2,673,000 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						 3,781,000 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						 4,573,000 
				 | 
			 
			
				| 
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
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				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						Total stock-based compensation expense 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						 1,678,000 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						 2,673,000 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						 3,781,000 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						 4,573,000 
				 | 
			 
			
				| 
					 
						Tax benefit 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  — 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  — 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  — 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  — 
				 | 
			 
			
				| 
					 
						Stock-based compensation expense, net of tax 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				
					 
						 1,678,000 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				
					 
						 2,673,000 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				
					 
						 3,781,000 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				
					 
						 4,573,000 
				 | 
			 
		  
		
			 
		 
		
			We estimate the fair value of each option award on the date of grant using the Black-Scholes option valuation model. We then recognize the grant date fair value of each option as compensation expense ratably using the straight-line attribution method over the service period (generally the vesting period). The Black-Scholes model incorporates the following assumptions:
		 
		
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			Expected volatility – we estimate the volatility of our share price at the date of grant using a “look-back” period which coincided with the expected term, defined below. We believe using a “look-back” period which coincides with the expected term is the most appropriate measure for determining expected volatility. 
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				 ·
			 
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			Expected term – we estimate the expected term using the “simplified” method, as outlined in Staff Accounting Bulletin No. 107, “Share-Based Payment.” 
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				 ·
			 
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			Risk-free interest rate – we estimate the risk-free interest rate using the U.S. Treasury yield curve for periods equal to the expected term of the options in effect at the time of grant. 
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				 ·
			 
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			Dividends – we use an expected dividend yield of zero because we have not declared or paid a cash dividend, nor do we have any plans to declare a dividend. 
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			We used the following weighted-average assumptions to estimate the fair value of the options granted for the periods indicated:
		 
		
			 
		 
		
			
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				| 
					 
						  
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				 | 
				
					 
						For the three months ended June 30,  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						For the six months ended June 30,  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						  
				 | 
				
					 
						     
				 | 
				
					 
						2019 
				 | 
				
					 
						     
				 | 
				
					 
						2018 
				 | 
				
					 
						  
				 | 
				
					 
						     
				 | 
				
					 
						2019 
				 | 
				
					 
						     
				 | 
				
					 
						2018 
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						Expected volatility 
				 | 
				
					 
						  
				 | 
				
					 
						 108 
				 | 
				
					 
						%   
				 | 
				
					 
						 109 
				 | 
				
					 
						% 
				 | 
				
					 
						  
				 | 
				
					 
						 108 
				 | 
				
					 
						%   
				 | 
				
					 
						 109 
				 | 
				
					 
						% 
				 | 
			 
			
				| 
					 
						Expected term 
				 | 
				
					 
						  
				 | 
				
					 
						5 years 
				 | 
				
					 
						  
				 | 
				
					 
						5 years 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						5 years 
				 | 
				
					 
						  
				 | 
				
					 
						5 years 
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						Risk-free interest rate 
				 | 
				
					 
						  
				 | 
				
					 
						 2.21 
				 | 
				
					 
						%   
				 | 
				
					 
						 2.65 
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						% 
				 | 
				
					 
						  
				 | 
				
					 
						 2.24 
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						%   
				 | 
				
					 
						 2.44 
				 | 
				
					 
						% 
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				| 
					 
						Expected dividend yield 
				 | 
				
					 
						  
				 | 
				
					 
						  — 
				 | 
				
					 
						%   
				 | 
				
					 
						  — 
				 | 
				
					 
						% 
				 | 
				
					 
						  
				 | 
				
					 
						  — 
				 | 
				
					 
						%   
				 | 
				
					 
						  — 
				 | 
				
					 
						% 
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			The following table summarizes the options granted for the periods indicated:
		 
		
			 
		 
		
			
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				 | 
				
					 
						  
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				| 
					 
						  
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						For the three months ended 
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						For the six months ended 
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				| 
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						June 30, 
				 | 
				
					 
						  
				 | 
				
					 
						June 30, 
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				| 
					 
						  
				 | 
				
					 
						     
				 | 
				
					 
						2019 
				 | 
				
					 
						     
				 | 
				
					 
						2018 
				 | 
				
					 
						     
				 | 
				
					 
						2019 
				 | 
				
					 
						     
				 | 
				
					 
						2018 
				 | 
			 
			
				| 
					 
						Options granted 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						 1,183,890 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						 224,800 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						 1,384,890 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						 869,800 
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				| 
					 
						Weighted-average: 
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				 | 
				
					 
						  
				 | 
				
					 
						   
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						   
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						   
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						   
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				| 
					 
						Exercise price 
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				 | 
				
					 
						$ 
				 | 
				
					 
						 6.86 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				
					 
						 16.27 
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						$ 
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						 6.84 
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						$ 
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						 14.38 
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				| 
					 
						Grant date fair value 
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				 | 
				
					 
						$ 
				 | 
				
					 
						 5.39 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				
					 
						 12.87 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				
					 
						 5.37 
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				 | 
				
					 
						$ 
				 | 
				
					 
						 11.36 
				 | 
			 
		  
		
			 
		 
		
			The following table summarizes restricted common stock compensation expense for the three and six months ended June 30, 2019 and 2018:
		 
		
			 
		 
		
			
				| 
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						For the three months ended June 30,  
				 | 
				
					 
						  
				 | 
				
					 
						For the six months ended June 30,  
				 | 
			 
			
				| 
					 
						  
				 | 
				
					 
						     
				 | 
				
					 
						2019 
				 | 
				
					 
						     
				 | 
				
					 
						2018 
				 | 
				
					 
						     
				 | 
				
					 
						2019 
				 | 
				
					 
						     
				 | 
				
					 
						2018 
				 | 
			 
			
				| 
					 
						Research and development 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				
					 
						  — 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				
					 
						  — 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				
					 
						  — 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				
					 
						  — 
				 | 
			 
			
				| 
					 
						General and administrative 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						 78,000 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						 172,000 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						 250,000 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						 344,000 
				 | 
			 
			
				| 
					 
						Stock-based compensation expense included in operating expense 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						 78,000 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						 172,000 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						 250,000 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						 344,000 
				 | 
			 
			
				| 
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
			 
			
				| 
					 
						Total stock-based compensation expense 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						 78,000 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						 172,000 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						 250,000 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						 344,000 
				 | 
			 
			
				| 
					 
						Tax benefit 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  — 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  — 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  — 
				 | 
				
					 
						  
				 | 
				
					 
						  
				 | 
				
					 
						  — 
				 | 
			 
			
				| 
					 
						Stock-based compensation expense, net of tax 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				
					 
						 78,000 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				
					 
						 172,000 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				
					 
						 250,000 
				 | 
				
					 
						  
				 | 
				
					 
						$ 
				 | 
				
					 
						 344,000 
				 | 
			 
		  
		
			 
		 
		
			We did not grant any common stock to directors or employees during the three and  six months ended June 30, 2019 or 2018.
		 
   
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