SELLAS Life Sciences Group (SLS) Proxy Filing summary

Voting matters and shareholder proposals

• Proposal 2 now seeks ratification of Baker Tilly as the independent registered public accounting firm for 2025, following the merger with Moss Adams.

• Votes previously cast for or against Proposal 2 will be counted as votes for or against Baker Tilly's ratification.

• No new proxy cards or voting instructions are required unless shareholders wish to change their vote.

• Proxy materials are available electronically, and shareholders can vote by Internet, phone, or mail until June 16, 2025.

• Shareholders may also vote during the annual meeting if they are stockholders of record and follow the provided instructions.

Audit committee and external auditor matters

• Moss Adams resigned as auditor after merging with Baker Tilly; Baker Tilly was appointed as the new auditor for 2025.

• Moss Adams' audit reports for 2023 and 2024 had no adverse opinions but included a going concern explanatory paragraph.

• No disagreements or reportable events occurred between the company and Moss Adams during the relevant periods.

• Moss Adams was provided a copy of the Form 8-K and its response was filed as Exhibit 16.1.

• The company did not consult Baker Tilly on accounting matters prior to their appointment.

Risk oversight and compliance

• The audit committee managed the transition between audit firms and ensured regulatory compliance in the process.

• Shareholders were informed of the auditor change and voting implications through a supplement and SEC filings.