Alligator Bioscience

• Presentation highlights ATOR-4066's superior anti-tumor effect and confirms CEACAM5-conditional activation of CD40 expressing cells
• Data show immunological memory displayed in vivo and homologous tumors cleared upon rechallenge
• Enhanced effect of ATOR-4066 when combined with anti-PD-1
• Data strongly emphasize the potential of ATOR-4066 as monotherapy and as a checkpoint inhibitor combination partner

Lund, Sweden – Alligator Bioscience (Nasdaq Stockholm: ATORX) today announces a poster presentation on ATOR-4066, a Neo-X-Prime™ bispecific antibody targeting CD40 and CEACAM5, at the 2023 SITC (Society for Immunotherapy of Cancer) Annual Meeting, being held in San Diego November 1-5, 2023.

The presentation, entitled "Combination treatment with ATOR-4066, a Neo-X-Prime™ bispecific antibody targeting CD40 and CEACAM5, and anti-PD-1 reverses T cell exhaustion in vitro", outlines the use of CEACAM5 expressing tumor models to study the anti-tumor efficacy of ATOR-4066 and to analyze induction of immunological memory in vivo.

The presentation highlights that:

• ATOR-4066 has a superior anti-tumor effect compared to a CD40 monospecific antibody
• ATOR-4066 activation of CD40 expressing cells is CEACAM5-conditional with no activation in absence of CEACAM5 indicating a potential for a wide therapeutic window
• ATOR-4066 is well positioned, with distinct advantages compared to other CD40 or CEACAM5 targeting therapies, such as strong anti-tumor effect in vivo also in larger tumors with heterogenous CEACAM5 expression
• ATOR-4066 induces immunological memory in vivo and were able to clear homologous tumors upon re-challenge
• Combining ATOR-4066 with anti-PD-1 in vitro in a mixed lymphocyte reaction assay[1] produces a clear synergistic effect observed on reactivation of exhausted T cells as measured by an increase in interferon gamma production
• Using dissociated tumor cells from gastric cancer patients, ATOR-4066 induced activation of multiple tumor infiltrating immune cell populations (i.e. B cells, macrophages and T cells)

"To have this abstract accepted for presentation at this year's prestigious SITC annual meeting is a testament both to the promise of ATOR-4066 and to the diligent work of the Alligator scientific team," said Søren Bregenholt, CEO of Alligator Bioscience. "These data emphasize the potential of ATOR-4066 both as a monotherapy and as a combination partner for checkpoint inhibitors to further enhance the immune response in tumors and we continue to advance ATOR-4066 towards the clinic."

Poster Presentation Details
Abstract Number: 837
Title: Combination treatment with ATOR-4066, a Neo-X-Prime™ bispecific antibody targeting CD40 and CEACAM5, and anti-PD-1 reverses T cell exhaustion in vitro
Date/Time: Friday 3 November, 2023, 9.00 am - 7.00 pm PDT
Presenter: Ida Uddbäck, Scientist, Alligator Bioscience
Location: Exhibit Halls A and B1, San Diego Convention Center

[1] Mixed lymphocyte reaction (MLR) – a common method for assessing the cellular immune response.