Artios doses first patient in Phase 2 POLKA trial of ART6043
Artios Pharma has dosed the first patient in its randomised Phase 2 POLKA study, evaluating the company's DNA Polymerase Theta (Polθ) inhibitor ART6043 in combination with the PARP inhibitor olaparib. The global, multicentre trial targets adults with germline BRCA-mutated (gBRCAm), HER2-negative locally advanced or metastatic breast cancer who are eligible to receive a PARP inhibitor.
The study, registered as NCT05898399, is enrolling 80 patients in a 1:1 randomisation to ART6043 plus olaparib or olaparib alone. The primary endpoint is progression-free survival; secondary endpoints include overall response rate, overall survival, and the rate of BRCA reversion mutations — the last of these being a notable inclusion, given that reversion mutations are an established mechanism of acquired resistance to PARP inhibition. Eligible patients may have received up to three prior lines of chemotherapy and no more than one month of prior PARP inhibitor treatment.
Clinical rationale
The mechanistic case for the combination rests on synthetic lethality logic. PARP inhibitors impair one strand-break repair pathway; ART6043 targets a distinct, complementary route — microhomology-mediated end joining (MMEJ), which is mediated by Polθ. Artios argues that cancer cells with BRCA mutations become doubly dependent on error-prone repair, and that blocking Polθ alongside PARP should increase cancer cell killing whilst potentially blunting the emergence of olaparib resistance.
ART6043 is described as orally bioavailable and selective for the polymerase domain of Polθ, an enzyme that the company says is preferentially expressed in tumour cells but largely absent in healthy tissue — a selectivity profile that, if borne out clinically, could differentiate it on tolerability. Phase 1/2a data, presented at the ESMO Congress in 2025, showed what Artios characterises as an attractive tolerability profile, expected pharmacokinetic and pharmacodynamic activity, and early clinical signals. The FDA granted ART6043 Fast Track designation in February 2026 for this combination and patient population.
Ian Smith, Chief Medical Officer of Artios, said the POLKA study initiation was "a significant step in realising the potential of ART6043 and advancing a new class of targeted therapies" for patients with gBRCAm HER2-negative breast cancer, adding that current treatment options beyond existing standards of care remain limited.
Market and competitive context
The PARP inhibitor market is well-established, with olaparib (AstraZeneca/MSD), niraparib (GSK) and talazoparib (Pfizer) all approved in BRCA-mutated breast cancer. The clinical question is what comes after PARP inhibitor failure or alongside it. The Polθ inhibitor class is attracting serious attention as one answer: Ideaya Biosciences is also advancing a Polθ inhibitor, IDE161, in clinical studies, meaning Artios faces emerging competitive pressure in what remains an early-stage field.
Artios positions ART6043 as the most advanced Polθ inhibitor in randomised clinical development — a claim the POLKA trial itself is designed to test against a PARP inhibitor control arm. Whether a randomised Phase 2 readout will be sufficient to support a regulatory filing, or whether a Phase 3 study will be required, will likely be shaped by the strength of the progression-free survival signal and discussions with the FDA under the Fast Track framework.
The Cambridge and New York-based company also holds an ATR inhibitor programme (alnodesertib) and a preclinical DDR inhibitor–ADC portfolio, giving it a degree of pipeline diversification should ART6043 encounter headwinds. Near-term milestones to watch include interim safety data from POLKA and any update on enrolment pace across the multicentre network.