CCCC - Updated Phase 1 Data Continue To Support Pivotal Trial Plan

Research evidence excerpt

CCCC - Updated Phase 1 Data Continue To Support Pivotal Trial Plan

FLASH NOTE

June 11, 2026

Brad Canino brad.canino@guggenheimpartners.com CCCC - Updated Phase 1 Data Continue To Support

212 823 6558 Pivotal Trial Plan

Josh Boen

Joshua.Boen@guggenheimpartners.com

212 518 5345 Key Message: Updated cemsidomide (IKZF1/3 degrader) phase 1 myeloma data

in a poster today at EHA show a consistent profile with longer follow-up for

the previously disclosed n=73 sample size of late-line patients, which we believe

already supported the ongoing pivotal phase 2 trial in 4L+ myeloma. The 53%

(10/19) ORR at the 100ug RP2D remains the same, but a positive update shows 3CCCC

C4 Therapeutics, Inc. responses have deepened including 1 to a sCR. New details also show the ORR at this

Sector: Biotechnology dose was a consistent 53% (9/17) in patients who had received prior T cell-redirecting

therapies. The durability update shows ongoing responses now beyond a year for several

Company Update patients at the 75ug and 100ug doses, and 7 patients are still ongoing despite this clinical

Share Price $3.87 phase having concluded. We think these data should also increase confidence in CCCC's

ongoing or planned combinations with TCE, CD38, and PI, especially following the

BMY (covered by Seamus Fernandez) mezigdomide SUCCESSOR-2 data at ASCO26

Market Data showing how powerful these next-generation degraders can be in earlier lines of therapy

52-Week Range $1.36 - $4.60 (LINK). Management like how cemsidomide is positioned against mezigdomide for these

Shares Out (M) 110.6 multi-drug regimens because their data show a dose reduction that is cut in half (21%

Market Cap (M) $428 [4/19] vs. 42% [122/288]), plus the cemsidomide reduction is to 75ug that is also very