- 
        Signature
      
- 
        /s/ Mina Kim, Attorney-in-fact
      
      
- 
        Stock symbol
      
- 
        SLRN
      
      
- 
        Transactions as of
      
- 
        May 4, 2023
      
      
- 
        Transactions value $
      
- 
        $0
      
      
- 
        Form type
      
- 
        3
      
      
- 
        Date filed
      
- 
        5/4/2023, 06:43 PM
      
 
     
   
 
  
    Transactions Table
  
  
    
      
        
          | Type | Sym | Class | Transaction | Value $ | Shares | Change % | * Price $ | Shares After | Date | Ownership | Footnotes | 
      
      
          
            | holding | SLRN | Class A Common Stock |  |  |  |  |  | 1.11M | May 4, 2023 | Direct | F1, F2 | 
          
            | holding | SLRN | Class A Common Stock |  |  |  |  |  | 678K | May 4, 2023 | See footnote | F1, F3 | 
          
            | holding | SLRN | Class A Common Stock |  |  |  |  |  | 355K | May 4, 2023 | See footnote | F1, F4 | 
          
            | holding | SLRN | Class A Common Stock |  |  |  |  |  | 355K | May 4, 2023 | See footnote | F1, F5 | 
          
            | holding | SLRN | Class A Common Stock |  |  |  |  |  | 350K | May 4, 2023 | See footnote | F1, F6 | 
          
            | holding | SLRN | Class A Common Stock |  |  |  |  |  | 5.07K | May 4, 2023 | See footnote | F1, F7 | 
      
    
   
  
    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 | 
      
      
          
            | holding | SLRN | Series B Redeemable Convertible Preferred Stock |  |  |  |  |  |  | May 4, 2023 | Class A Common Stock | 978K |  | See footnote | F1, F8, F9 | 
          
            | holding | SLRN | Series C Redeemable Convertible Preferred Stock |  |  |  |  |  |  | May 4, 2023 | Class A Common Stock | 183K |  | See footnote | F1, F8, F9 | 
      
    
   
  
    * An asterisk sign (*) next to the price indicates that the price is likely invalid.
  
  
    Explanation of Responses:
  
  
  
    Remarks:
  
  Exhibit 24 - Power of Attorney