Biomarker-Driven GUIDANCE Trial Targets HRD-Positive Small Cell Lung Cancer With Olaparib Plus Durvalumab
Clinical Summary:
- Design/Population: GUIDANCE is a biomarker-driven, multicenter, single-arm, phase 2 trial enrolling patients with advanced or metastatic small cell lung cancer (SCLC) without progression after first-line platinum, etoposide, and durvalumab. Enrollment requires HRD, defined by pathogenic homologous recombination repair gene alterations and/or a genomic instability score ≥40.
- Key Outcomes: The trial will enroll 29 patients who will receive 1500 mg of durvalumab every 4 weeks plus 300 mg of olaparib twice daily until progression or unacceptable toxicity. The primary end point is progression-free survival, with overall survival, safety, tolerability, immune-related responses, circulating tumor DNA, SLFN11 expression, and immune-cell composition evaluated as secondary or exploratory measures.
- Clinical Relevance: GUIDANCE tests whether prospective HRD selection can identify a subset of patients with SCLC more likely to benefit from PARP inhibition combined with ongoing PD-L1 blockade, potentially establishing a chemotherapy-free and molecularly guided maintenance strategy in a disease that currently lacks validated predictive biomarkers.
The phase 2 GUIDANCE trial is evaluating a biomarker-selected maintenance strategy with olaparib plus durvalumab in patients with advanced or metastatic small cell lung cancer (SCLC) whose disease has not progressed after first-line platinum, etoposide, and durvalumab.
“SCLC currently lacks validated predictive biomarkers to identify patients most likely to benefit from immunotherapy or targeted approaches,” stated Richard Riedel, MD, University Hospital Cologne, Cologne, Germany, and coauthors. “Treatment remains largely unselected, highlighting a substantial unmet need for novel therapeutic strategies and biomarker-driven approaches in this aggressive disease.”
This multicenter, single-arm study is designed to enroll 29 patients across 5 centers in Germany following centralized prescreening. Eligibility requires newly diagnosed extensive-stage SCLC or limited-stage disease not amenable to curative chemoradiotherapy, no progression after 4 cycles of platinum, etoposide, and durvalumab, an ECOG performance status of 0 or 1, and confirmed HRD.
HRD is defined by the presence of pathogenic class 4 or 5 alterations in homologous recombination repair genes and/or a genomic instability score of at least 40. Approximately 30% of patients with SCLC are expected to meet the study’s HRD criteria.
Patients will receive 1500 mg of durvalumab every 4 weeks plus 300 mg of olaparib twice daily in 28-day cycles until disease progression, unacceptable toxicity, or another reason for treatment discontinuation.
The primary end point is progression-free survival (PFS) by RECIST 1.1. The study assumes a historical median PFS of 2.6 months as the null hypothesis and is designed to detect an improvement to 3.6 months. Overall survival (OS), immune-related responses, safety, tolerability, dose modifications, and relative dose intensity are secondary end points.
The study also incorporates multiple translational analyses intended to refine biomarker selection. SLFN11 expression will be evaluated as a potential predictor of PARP inhibitor sensitivity and compared with HRD status. ctDNA will be monitored through patient-specific TP53 mutations, while multiplex immunohistochemistry will assess tumor-infiltrating immune-cell composition and its association with clinical outcomes.
The rationale for the combination is based on the potential interaction between DNA damage repair deficiency and immune evasion. Olaparib targets PARP-mediated DNA repair, while durvalumab maintains PD-L1 blockade following first-line chemoimmunotherapy. The investigators hypothesize that prospective HRD selection may identify patients more likely to benefit from this combination than the unselected populations included in previous PARP inhibitor studies.
The strategy is also intended to avoid additional cytotoxic chemotherapy during maintenance. The investigators noted that prior studies combining PARP inhibition with chemotherapy or immunotherapy produced limited efficacy or greater toxicity, potentially because they enrolled molecularly unselected populations.
GUIDANCE will also explore whether SLFN11 may complement or outperform conventional genomic HRD measures as a marker of PARP inhibitor sensitivity in SCLC. This is particularly relevant because pathogenic homologous recombination repair gene alterations are relatively uncommon in the disease.
“This trial investigates a chemotherapy-free, genomically stratified maintenance strategy targeting both DNA damage repair deficiency and immune evasion in SCLC,” concluded Dr Riedel et al. “By integrating HRD-based patient selection with concurrent PARP and immune checkpoint inhibition, GUIDANCE aims to establish a more individualized therapeutic approach and to generate a signal for further evaluation in biomarker-defined patient populations.”
Source:
Riedel R, Verheyen M, Michels S, et al. Rationale and study design of the GUIDANCE trial: A multicenter phase II trial of maintenance durvalumab and olaparib after standard 1st line treatment (carboplatin/cisplatin, etoposide, durvalumab) in HRD positive extensive disease (ED) small-cell lung cancer (SCLC) (AIO-TRK-0124/ass). Clin Lung Cancer. Published online: August 11, 2026. doi: 10.1016/j.cllc.2026.08.001
