SL-325 Surpassed Street Expectations & Smart SL-846 Bispecific Development

Research evidence excerpt

SL-325 Surpassed Street Expectations & Smart SL-846 Bispecific Development

C O M PA N Y N O T E

J u n e 8 , 2 0 2 6

Exhibit 1 - SL-325 Showed a Potentially Best-in-Mechanism Immunogenecity Profile

Source: STTK Company Materials

"*ADA rates are provided as they were reported in the referenced publications/reports. These data were

not generated in head-to-head clinical trials. Comparisons across trials have inherent limitations and

caution should be exercised when comparing data from unrelated studies"

SL-325 showed strong durability with full DR3 occupancy achieved even at the lowest

dose of 0.1 mg/kg. Moreover, STTK presented PK data from SL-325's Ph1 (NCT07158437)

where Exhibit 2 demonstrated dose proportional increases and an estimated half-life of 16

days. Specifically, mgmt presented patient-level SAD PK data given its consistency across dose

groups where distinct increases in Cmax and AUClast were observed across all dose levels

(0.1 to 30 mg/kg). Hence, we believe these data support SL-325's durable and predictable

product profile where clearance was consistent across dose levels with an accumulation ratio

between 1.64-1.75 with repeat dosing. To further substantiate SL-325's differentiated product

profile, receptor occupancy data (Exhibit 3) showed a single dose of SL-325 was able to block

TL1A binding in a dose-dependent manner for months. With this, DR3 occupancy was measured

by inhibition of TL1A binding where full DR3 occupancy was achieved even at the lowest dose

of 0.1 mg/kg. Importantly, a dose-dependent extension of the TL1A blockade duration was also

observed and lasted months at doses ≥1 mg/kg. Thus, SL-325 has the potential for quarterly

dousing intervals during the maintenance phase of treatment. As such, mgmt expressed they

Shattuck Labs, Inc.