McCarthy Sean A. 4

What Happened
Sean A. McCarthy, CEO and Director of CytomX Therapeutics (CTMX), sold 118,969 shares on March 17, 2026 at $6.42 per share, generating proceeds of $764,138. The sale was marked as to satisfy tax or other government withholding obligations in connection with the vesting of restricted stock units (RSUs), so it is a routine, non-investment-motivated sale rather than a new purchase.

Key Details

• Transaction date: 2026-03-17; Price: $6.42 per share; Shares sold: 118,969; Proceeds: $764,138. (Transaction code: S = Sale)
• Purpose: Sold solely to satisfy tax/government withholding obligations tied to RSU vesting (Footnote F1).
• Holdings referenced: filing notes inclusion of 457,500 RSUs (F2) and shares held by the Sean A. McCarthy 2018 Trust, of which he is trustee (F3).
• Shares owned after transaction: not specified in the Form 4 filing.
• Timeliness: Form 4 filed 2026-03-19 for a 2026-03-17 trade — filed within the usual Section 16 reporting window.

Context
This was a sale to cover tax withholding on vested RSUs (common executive administrative activity) rather than an open-market purchase indicating increased insider confidence. No 10b5-1 plan or other trading plan was referenced in the provided footnotes.