| STOCK-BASED COMPENSATION (Tables)
 | 6 Months Ended | 
| Jun. 30, 2021 | 
|---|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  | 
| SCHEDULE OF STOCK BASED COMPENSATION | Stock
Options: The following table summarizes stock option-based compensation for the three and six months ended June 30, 2021 and 2020:  SCHEDULE OF STOCK BASED COMPENSATION 
  
    |  |  | For the three months ended June 30, |  |  | For the six months ended June 30, |  |  
    |  |  | 2021 |  |  | 2020 |  |  | 2021 |  |  | 2020 |  |  
    | Research and development |  | $ | 608,000 |  |  | $ | 871,000 |  |  | $ | 1,217,000 |  |  | $ | 1,615,000 |  |  
    | General and administrative |  |  | 719,000 |  |  |  | 707,000 |  |  |  | 1,193,000 |  |  |  | 1,219,000 |  |  
    | Stock option-based compensation expense included in operating expense |  | $ | 1,327,000 |  |  | $ | 1,578,000 |  |  | $ | 2,410,000 |  |  | $ | 2,834,000 |  |    | 
| SCHEDULE OF WEIGHTED-AVERAGE ASSUMPTIONS TO ESTIMATE THE FAIR VALUE OF THE OPTIONS GRANTED | We
used the following weighted-average assumptions to estimate the fair value of the options granted for the periods indicated:  SCHEDULE OF WEIGHTED-AVERAGE ASSUMPTIONS TO ESTIMATE THE FAIR VALUE OF THE OPTIONS GRANTED 
  
    |  |  | For the three months ended June 30, |  |  | For the six months ended June 30, |  |  
    |  |  | 2021 |  |  | 2020 |  |  | 2021 |  |  | 2020 |  |  
    | Expected volatility |  |  | 97 | % |  |  | 111 | % |  |  | 98 | % |  |  | 111 | % |  
    | Expected term |  |  | 5.67 years |  |  |  | 6.25 years |  |  |  | 5.93 years |  |  |  | 6.25 years |  |  
    | Risk-free interest rate |  |  | 0.96 | % |  |  | 0.23 | % |  |  | 0.99 | % |  |  | 0.30 | % |  
    | Expected dividend yield |  |  | 0 | % |  |  | 0 | % |  |  | 0 | % |  |  | 0 | % |  | 
| SCHEDULE OF OPTIONS ACTIVITY | The
following table summarizes the options granted for the periods indicated:  SCHEDULE OF OPTIONS ACTIVITY 
  
    |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
    |  |  | For the three months ended June 30, |  |  | For the six months ended June 30, |  |  
    |  |  | 2021 |  |  | 2020 |  |  | 2021 |  |  | 2020 |  |  
    | Options granted |  |  | 1,205,808 |  |  |  | 1,897,119 |  |  |  | 3,355,308 |  |  |  | 3,073,046 |  |  
    | Weighted-average: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
    | Exercise price |  | $ | 1.60 |  |  | $ | 2.83 |  |  | $ | 2.05 |  |  | $ | 2.30 |  |  
    | Grant date fair value |  | $ | 1.22 |  |  | $ | 2.36 |  |  | $ | 1.59 |  |  | $ | 1.92 |  |  | 
| SUMMARY OF RESTRICTED COMMON STOCK | The
following table summarizes the restricted common stock granted for the periods indicated:  SUMMARY
OF RESTRICTED COMMON STOCK 
  
    |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
    |  |  | For the three months ended June 30, |  |  | For the six months ended June 30, |  |  
    |  |  | 2021 |  |  | 2020 |  |  | 2021 |  |  | 2020 |  |  
    | Restricted common stock granted |  |  | 926,484 |  |  |  | 1,083,313 |  |  |  | 1,975,734 |  |  |  | 1,083,313 |  |  
    | Restricted common stock forfeited |  |  | (220,136 | ) |  |  | - |  |  |  | (428,659 | ) |  |  | - |  |  
    | Weighted-average: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
    | Grant date fair value-granted awards |  | $ | 1.60 |  |  | $ | 3.19 |  |  | $ | 1.97 |  |  | $ | 3.19 |  |  
    | Grant date fair value-forfeited awards |  | $ | 2.05 |  |  | $ | - |  |  | $ | 1.89 |  |  | $ | - |  |  | 
| Restricted Stock [Member] |  | 
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  | 
| SCHEDULE OF STOCK BASED COMPENSATION | Restricted
Common Stock: The following table summarizes restricted common stock compensation expense for the three and six months ended June
30, 2021 and 2020:  SCHEDULE OF STOCK BASED COMPENSATION 
  
    |  |  | For the three months ended June 30, |  |  | For the six months ended June 30, |  |  
    |  |  | 2021 |  |  | 2020 |  |  | 2021 |  |  | 2020 |  |  
    | Research and development |  | $ | 484,000 |  |  | $ | 147,000 |  |  | $ | 1,030,000 |  |  | $ | 472,000 |  |  
    | General and administrative |  |  | 617,000 |  |  |  | 40,000 |  |  |  | 938,000 |  |  |  | 179,000 |  |  
    | Restricted stock-based compensation expense included in operating expense |  | $ | 1,101,000 |  |  | $ | 187,000 |  |  | $ | 1,968,000 |  |  | $ | 651,000 |     |  |