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        Signature
      
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        /s/ Thomas P. O'Neil as Attorney in Fact for Heath Lukatch, Ph.D.
      
      
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        Stock symbol
      
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        STSA
      
      
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        Transactions as of
      
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        Jun 8, 2023
      
      
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        Transactions value $
      
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        $0
      
      
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        Form type
      
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        4
      
      
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        Date filed
      
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        6/8/2023, 04:31 PM
      
 
     
   
 
  
    Derivative Securities (e.g., puts, calls, warrants, options, convertible securities)
  
  
    
      
        
          | Type | Sym | Class | Transaction | Value $ | Shares | Change % | * Price $ | Shares After | Date | Underlying Class | Amount | Exercise Price | Ownership | Footnotes | 
      
      
          
            | transaction | STSA | Stock Option (right to buy) | Disposed to Issuer | $0 | -20K | -100% | $0.00* | 0 | Jun 8, 2023 | Common Stock | 20K | $27.97 | Direct | F1, F2 | 
          
            | transaction | STSA | Stock Option (right to buy) | Disposed to Issuer | $0 | -20K | -100% | $0.00* | 0 | Jun 8, 2023 | Common Stock | 20K | $4.60 | Direct | F1, F2 | 
          
            | transaction | STSA | Stock Option (right to buy) | Disposed to Issuer | $0 | -30K | -100% | $0.00* | 0 | Jun 8, 2023 | Common Stock | 30K | $3.46 | Direct | F1, F2 | 
      
    
   
  
    * An asterisk sign (*) next to the price indicates that the price is likely invalid.
  
  Heath Lukatch is no longer subject to Section 16 filing requirements. Form 4 or Form 5 obligations may continue.
  
    Explanation of Responses: