Artios Announces Phase 1/2a Data for DNA Polymerase Theta Inhibitor ART6043 at ESMO Congress 2025

• Potential first-in-class, and industry-leading DNA polymerase Theta (Polθ) inhibitor, ART6043 demonstrated an attractive tolerability profile, expected PK/PD activity, and promising clinical signals
• Results support the potential advancement of ART6043 into Phase 2 clinical development

CAMBRIDGE, United Kingdom and NEW YORK, October 17, 2025 – Artios Pharma Limited (“Artios”), a biopharmaceutical company committed to realizing the therapeutic power of targeting the DNA damage response (“DDR”) in cancer, today announced the first clinical data from its Phase 1/2a study (NCT05898399) of its novel DNA polymerase Theta (Polθ) inhibitor, ART6043. The data were featured in an oral presentation at the European Society for Medical Oncology (ESMO) Congress 2025 in Berlin by Principal Investigator Dr. Timothy A. Yap, VP and Head of Clinical Development in the Therapeutics Discovery Division at The University of Texas MD Anderson Cancer Center. The results highlighted ART6043 in combination with the PARP inhibitor, olaparib, in patients with advanced solid tumors harboring mutations in a DNA damage response pathway.

ART6043 targets Polθ, a key DNA repair enzyme that is overexpressed in many cancers but present at low levels or absent in most healthy tissues. Cancer cells rely on Polθ as a backup DNA repair mechanism to survive when their primary homologous recombination (HR) DNA repair pathway is defective or when they acquire resistance to DNA-damaging therapies such as PARP inhibitors. By blocking Polθ, ART6043 is designed to shut down this alternative repair route, rendering tumors unable to effectively repair DNA damage and thereby enhancing anti-tumor activity.

“The emerging clinical data validate our approach to inhibit Polθ to selectively cripple tumor cells and exploit a cancer’s dependency on DNA repair,” said Ian Smith, Chief Medical Officer of Artios. “The initial data and efficacy signals in the relevant genetic background are encouraging, and we look forward to advancing ART6043’s clinical development to realize its potential to increase the effectiveness of PARP inhibition, where resistance to standard of care has become increasingly prevalent.”

Summary of Key Clinical Results:

• Baseline characteristics
  
  • ART6043 Monotherapy: 19 patients; median age: 58 years; prior treatment with PARP inhibitor: 37%
  • ART6043+olaparib: 42 patients; median age: 65.5 years; prior treatment with PARP inhibitor: 31%
  • All patients received a median of 4 prior therapies
• Highlights of clinical data presented at ESMO 2025
  
  • ART6043 demonstrated an expected, benign tolerability profile as a monotherapy, with no additional toxicity to that of olaparib when combined
  • Pharmacokinetic data support convenient and oral once-daily dosing, and no drug-drug interaction (DDI) between ART6043 and olaparib was observed
  • Pharmacodynamic engagement of ART6043 alone was enhanced in combination with olaparib in patients, and was similar to preclinical models where tumor regressions were seen

“The first-in-class Polθ inhibitor, ART6043, represents a much-needed therapeutic option for patients with advanced, hard-to-treat cancers where resistance to existing treatments is a major clinical challenge,” said Dr. Timothy A. Yap, Principal Investigator of the study. “The initial clinical signals observed to date reinforce the potential of ART6043 to address this significant unmet need for patients who currently have limited treatment options. I look forward to the further evaluation of Polθ inhibition as additional clinical data become available.”

ART6043 continues to be evaluated in a first-in-human Phase 1/2a study in patients with advanced solid tumors. ART6043 has the potential to advance into dedicated Phase 2 trials to assess efficacy across molecularly selected cohorts and expand its potential into new combinations and disease settings.

The full abstracts will be published in the ESMO Congress 2025 Abstract Book, a supplement to the official ESMO journal, Annals of Oncology.

About ART6043
ART6043 is a potential first-in-class, selective, orally bioavailable, small‑molecule inhibitor of the polymerase domain of DNA polymerase theta (Polθ), a DNA repair enzyme that is preferentially expressed in cancer cells but is virtually absent in most healthy tissues. By inhibiting Polθ, ART6043 targets microhomology‑mediated end joining (MMEJ) to exploit tumor dependence on error‑prone DNA repair, with broad rationale for use as monotherapy and in combination with PARP inhibition and other DNA‑damaging modalities. Artios’ differentiated approach is evaluating ART6043 with olaparib in molecularly defined solid tumors, including settings of BRCA variants and PARP inhibitor resistance, to enhance target engagement and anti-tumor activity while maintaining tolerability.

About Artios Pharma Ltd.
Artios is pioneering approaches in the DNA damage response (DDR) field through its comprehensive anti-cancer approach and the deep experience of its team of DDR drug developers. The company’s clinical-stage candidates, ATR inhibitor alnodesertib and DNA Polymerase theta (Polθ) inhibitor ART6043, as well as its pre-clinical programs, including DDRi-ADCs, are designed with differentiated pharmaceutical properties and novel biological approaches to precisely eliminate a cancer cell’s remaining survival mechanisms. Artios’ mission is to develop new classes of medicines that exploit DDR pathways with the aim of improving outcomes for patients with hard-to-treat cancers.

Visit our website at www.artios.com for more information about the company.

For more information, please contact:
Trophic Communications
Jacob Verghese or Verena Schossmann
Tel: +49 151 7441 6179
Email: artios@trophic.eu