Article Text

Download PDFPDF

1079 LAG3-targeted IL15/IL15Rα-Fc (LAG3 x IL15) fusion proteins for preferential TIL expansion via cis delivery of IL15 to LAG3+ cells
  1. Matthew Bernett,
  2. Suzanne Schubbert,
  3. Michael Hackett,
  4. Lukasz Ochyl,
  5. Lizett Scott,
  6. Christine Bonzon,
  7. Rumana Rashid,
  8. Kendra Avery,
  9. Nicole Rodriguez,
  10. Irene Leung,
  11. Norman Barlow,
  12. Rena Bahjat,
  13. Umesh Muchhal and
  14. John Desjarlais
  1. Xencor, Inc., Monrovia, CA, USA


Background Therapeutic approaches utilizing IL2 or IL15 have suffered from low tolerability, fast clearance, and limited therapeutic window due to extensive activity on peripheral T and NK cells. Conversely, selective targeting of tumor-reactive lymphocytes (TIL) may improve tolerability and anti-tumor activity while simultaneously improving drug PK. We hypothesized that we could selectively target tumor-reactive TILs by combining a reduced potency IL15/IL15Rα heterocomplex with an immune checkpoint(CP)-targeting arm to bias binding and activation to CP-positive TILs, potentially improving therapeutic index. Lymphocyte activation gene 3 (LAG3) was chosen as the CP targeting-arm due to its frequent co-expression with PD1, bias to CD8+ T cells, ability to easily combine with anti-PD1 agents, and recent promising results with anti-LAG3 agents in the clinic.

Methods First, potency-reduced IL15/IL15Rα were created by engineering amino acid substitutions in IL15 – at the IL2Rβ/γc interface – that reduced in vitro potency by at least 1000-fold. We then designed LAG3 x IL15 fusion proteins containing single-chain IL15/IL15Rα and LAG3-targeting arms attached to a heterodimeric-Fc region, relying on targeting avidity (in cis) to recover potency on LAG3+ cells. In vitro proliferation of lymphocytes in human PBMCs, stimulated with sub-optimal concentrations of anti-CD3 to induce LAG3 expression, was monitored by CFSE dilution or by counting Ki67+ cells after incubation with LAG3 x IL15. In vivo activity was evaluated using a humanized mouse tumor model. Lead LAG3 x IL15 were evaluated in non-human primates (NHP).

Results LAG3 x IL15 showed >500-fold selectivity compared to a non-targeted IL15 in an in vitro proliferation assay of lymphocytes stimulated for induced LAG3 expression. In vitro potency was greatest on effector memory CD8 T cells. LAG3 x IL15 were 3-fold more potent on CD8 T cells compared to CD4 T cells and had very weak activity on NK cells, consistent with minimal LAG3 expression on this population. In mouse tumor models, LAG3 x IL15 had single-agent anti-tumor activity and promoted significantly increased numbers of T cells. Moreover, LAG3 x IL15 combined productively with anti-PD1 to promote additional anti-tumor activity and T cell expansion. In NHP, LAG3 x IL15 has superior PK compared to native IL15-Fc and showed selective targeting of LAG3+ peripheral T cells.

Conclusions LAG3 x IL15 shows a promising profile of selective delivery to LAG3+ cells with minimal peripheral activity and may help to preferentially expand LAG3+ TIL in patients with cancer, while potentially avoiding systemic toxicity due to off-target activation and expansion of peripheral lymphocytes.

Statistics from

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.