C4 Therapeutics (CCCC) investor relations material

Clinical program updates

• Two active clinical programs: cemsidomide (IKZF1/3 degrader) and CFT8919 (EGFR L858R degrader) are progressing, with cemsidomide moving to the next phase early next year and CFT8919 in a phase one study in China.

• Cemsidomide phase one data showed a 36% ORR overall, with 40% and 53% ORR at the two highest doses; two CRs observed at 100 mcg, and a median treatment duration of 9.3 months.

• Safety profile for cemsidomide is favorable, with no discontinuations due to safety and only 6% dose reductions; most DLTs at 100 mcg were not drug-related.

• Patient population was highly refractory: 100% triple-class exposed, 75% had prior CAR T or T-cell engager therapy, with consistent response rates across subgroups.

• Cross-trial comparison shows cemsidomide efficacy and safety competitive with mezigdomide, with a more refractory patient population and fewer neutropenic complications.

Development and regulatory plans

• No further phase one disclosures planned; next update expected after FDA meeting on dose selection later this month, with phase two enrollment and dosing targeted for early next year.

• Type C FDA meeting provided feedback on development plans for the 4L+ trial; single-arm study could be approvable if robust, durable responses are maintained, though regulatory risk remains.

• 4L+ study will be global, with U.S. patients expected to be triple-class refractory and a mix of prior CAR T or BiTE exposure; aiming for a 40% ORR, a 20% improvement over background.

• Duration of response goal is to exceed six months, with current data showing 9.3 months median duration.

Pipeline, partnerships, and financials

• Delivered two development candidates to Biogen, with one in clinic and another expected soon; progress ongoing with Roche and Merck KGaA collaborations.

• CFT8919 program in China may reach a go/no-go decision by end of Q1 2026; future capital requirements for this program are still to be determined.

• Recent financing extends cash runway through end of 2028, not including up to $40 million in potential milestone payments from partners over 2026–2027.

• Key milestones include phase two MOMENTUM study data readouts in late 2027 (ORR by investigator) and later in 2028 (central assessment), plus updates from the phase 1b Elrexfio combination study as segments complete.