TherapeuticsConfidential1 TherapeuticsConfidential1

A STAT3-Selective Targeted Protein Degrader Decreases The Immune-Suppressive Tumor Microenvironment And Drives Anti-Tumor Activity In Preclinical Models

Fred Csibi, Bin Yang, Yogesh Chutake, Karen Yuan, Scott Rusin, Rahul Karnik, Veronica Campbell, Michele Mayo, Kirti Sharma, Haojing Rong, Henry Li, Sharon Townson, Hari Kamadurai, Mike Sintchak, Christine Loh, Alice McDonald, Anthony Slavin, Chris De Savi, Jared Gollob, Duncan Walker, Phillip Liu, Nan Ji and Nello Mainolfi. Kymera Therapeutics, Inc. 300 Technology Square, Cambridge, MA 02139. Contact: fcsibi@kymeratx.com

Introduction

Conclusions

Disclosures: Csibi, Yang, Yuan, Mayo, Chutake, Rong, Rusin, Karnik, Sharma, Campbell, Li, Townson, Kamadurai, Sintchak, McDonald, Slavin, De Savi, Liu, Gollob, Walker, Ji, Mainolfi. Kymera Therapeutics: Employment, Equity Ownership.

Figure 2- STAT3 Integrates Multiple Upstream Signaling Events To Regulate Tumor Intrinsic and Extrinsic Functions in The TME

LB-088

Figure 1 - Overview of Targeted Protein Degradation

BROAD OPPORTUNITYONLY BINDING SITE REQUIRED

EFFICIENTCATALYTIC

PROLONGED IMPACTTARGET PROTEIN DEGRADATION

HITCHING A RIDEUPS INTACT & FUNCTIONAL

Figure 3- KTX-201 Is a Potent and Selective STAT3 Degrader in Human Immune Cells Figure 5- STAT3 Degradation Reverses Immuno-Suppression in a Co-Culture Model of the Tumor Microenvironment in NSCLC

Figure 6- STAT3 Degrader Enhances Anti-Tumor Immunity in CT26 Colorectal TumorsFigure 4- STAT3 Degradation Downregulates Genes Involved with Immune Suppression in Both Immune and Tumor Cells

• STAT3 is a transcription factor downstream of several signaling events including the IL-6/JAK pathway that has been implicated in multiple aspects of tumorigenesis.

• In addition to increasing cancer cell proliferation and survival, constitutively activatedSTAT3 is proposed to regulate cross-talk interactions between tumor, stroma andimmune cells to promote immune evasion in the tumor microenvironment (TME).

• STAT3 activity in tumors promotes the production of immune-suppressive factors thatactivate STAT3 in diverse immune-cell subsets. Mechanistically, genetic studies supporta direct role of activated STAT3 in regulating myeloid cell differentiation to contribute toan immuno-suppressed TME.

• STAT3 is therefore a highly attractive target for immuno-oncology. However, potent andselective agents that specifically and directly target STAT3 have remained elusive.

• Kymera Therapeutics is developing degraders of STAT3 with drug-like properties,represented here with KTX-201 and its related compound KTX-104. These compoundspotently and selectively degrade STAT3 protein and reverse immuno-suppression inpreclinical models.

• Hyperactivation of STAT3 promotes tumor-intrinsic geneexpression programs involved with survival, proliferation,stemness and metastasis of tumor cells.

• Additionally, STAT3 promotes the differentiation and activity ofimmunosuppressive cells in the tumor microenvironment.

• STAT3 activation in endothelial cells contributes toangiogenesis.

STAT3Degrader

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Fig.3A- Degradation of STAT3 in immune cellsPBMCs, flow cytometry, 24hr

Immune cells STAT3 DC50 (nM) STAT3 DC90 (nM) Monocytes 0.15 1.25

Lymphocytes 5.4 14 KTX-201 (10X Lymphocyte DC90) / DMSO Average

pval=0.05

Fig. 3B- Selectivity in PBMCsDeep Tandem Mass Tag Proteomics, 8hr

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Fig. 4B- STAT3 degradation downregulates Pd-l1 mRNA in lymphoma (ALK+ ALCL)

Cell line STAT3, DC50 (nM) Pd-l1

mRNA IC50 (nM)

SU-DHL-1 11.7 14.3

SUP-M2 16.3 19.8

Fig. 4A- STAT3 degradation inhibits IL-6-dependent gene expression changes in human PBMCs(Nanostring analysis)

• KTX-201 decreases genes involved with immunosuppressive myeloid cells (e.g., CD163, a M2 macrophage marker) and changes in cytokine signaling (e.g, decrease in IL-10 and IL-17A and increase in TNF) as well as genes involved with survival and proliferation (e.g., decrease in Myc)

• Single Cells (FSC-A vs FSC-H)• Live-Dead vs SSC-A• CD45• CD4 vs CD8 (CD3 Gated)• M1 vs M2 Macrophages (CD11b, F4/80, CD206,

IA/IE Gated)

Fig. 6B- Strategy for Pharmacodynamic ImmunophenotypingKTX-201, 25mg/kg, 3 doses every 2 days. Tumor collection 24hr post last dose

• Kymera has developed potent and highly selective STAT3 degraders with activity in immune andtumor cells.

• STAT3 degradation inhibited IL-6-induced changes in gene expression involved with myeloid cellmarkers and cytokine signaling in immune cells and downregulated Pd-l1 mRNA in tumor cells.

• These results indicate that degrading STAT3 has the potential to reverse immune suppression bymodulating the composition and activity of immune cells in the TME and directly downregulatingimmune checkpoint signals in tumor cells.

• Kymera is advancing STAT3 degraders to clinical development in both liquid and solid tumors.

STAT3 degrader increases production of anti-tumoral factors IL-2, IFNg, and TNFa and reduces production of pro-tumoral factors VEGF and IL-6

Fig. 5C- STAT3 degrader reverses immuno-suppression with a profile distinct from JAK inhibitor

KTX-104

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Fig. 6C- STAT3 degrader increases anti-tumor (M1, CD8) and decreases immuno-suppressive (M2) infiltrates

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Fig. 5B- STAT3 degraders decreases STAT3 in H1299 cells without affecting cell growth

STAT3 DC50 = 30nM

• Human PBMCs (2 donors)• KTX-201, 400nM pre-treatment 18hr• IL-6 10ng/mL, 1 and 6hr

STAT3 Alexa FluorTM 647 staining:• Lymphocytes: CD8/CD4/CD19/CD56 (T/B/NK cells)• Monocytes: CD14

Fig. 5A- Co-culture model of human TMEBioMAP® NSCLC Oncology System (Eurofins Discovery)

Cytokine signalingImmune markers Survival/proliferationLog2-fold change KTX-201 vs DMSO

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Fig. 6A- STAT3 degraders shows anti-tumor activity at well tolerated doses in the syngeneic CT26 model

Tumor volume Body weightIn vitro CT26 DC50 (WB) at 24h = 14 nM

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SU-DHL-1 cells SUP-M2 cells

• KTX-201 decreases the levels of Pd-l1 gene consistent with a robust degradation of STAT3 in Anaplastic Large T Cell Lymphoma cells