Cardiff Oncology's Onvansertib Shows Promising Activity in RAS-Mutated mCRC

Cardiff Oncology's Onvansertib Shows Strong Efficacy in RAS-Mutated mCRC

Cardiff Oncology's Phase II CRDF-004 trial of onvansertib in RAS-mutated unresectable metastatic colorectal cancer (mCRC) demonstrated promising antitumor activity and an acceptable safety profile. Patients receiving first-line standard of care (SoC) chemotherapy (FOLFIRI or FOLFOX) plus bevacizumab were enrolled. The trial showed that onvansertib 30mg combined with FOLFIRI and bevacizumab achieved a confirmed objective response rate (ORR) of 72.2%, significantly higher than the 42.1% in the FOLFIRI plus bevacizumab control arm. Median progression-free survival (PFS) was not reached in the experimental arms compared to 10.97 months in the control, with a hazard ratio (HR) of 0.53. These encouraging results support the company's plan for a Phase III evaluation.

• Cardiff Oncology's onvansertib, when combined with FOLFIRI and bevacizumab, achieved a confirmed objective response rate (ORR) of 72.2% in RAS-mutated unresectable mCRC patients. This significantly outperformed the 42.1% ORR observed in the FOLFIRI plus bevacizumab control arm, indicating substantial antitumor activity in a patient population with high unmet needs.
• The trial demonstrated a notable improvement in progression-free survival (PFS) for patients treated with onvansertib (20mg and 30mg) plus FOLFIRI–bevacizumab. Median PFS in the experimental arms was not reached, compared to 10.97 months in the FOLFIRI plus bevacizumab control arm, resulting in a favorable hazard ratio (HR) of 0.53. This suggests a prolonged period without disease progression.
• Onvansertib exhibited a manageable safety profile, with neutropenia being the most common Grade 3 or higher adverse event. While per-arm sample sizes were small, the encouraging results have prompted Cardiff Oncology to announce a Phase III evaluation of onvansertib 30mg in combination with FOLFIRI and bevacizumab, aiming to confirm these findings and address the significant unmet need in RAS-mutant mCRC.

Onvansertib's Interim Data in RAS-Mutant mCRC

Recent clinical trials have demonstrated significant advances in metastatic colorectal cancer treatment across multiple therapeutic lines. These studies encompass novel immunotherapy combinations, HER2-targeted therapies, and optimized chemotherapy regimens, providing new treatment options for patients with limited therapeutic alternatives.

• STELLAR-303 (Zanzalintinib plus Atezolizumab vs Regorafenib) - Global phase 3 trial (n=901) in non-MSI-H/dMMR mCRC patients showed median OS of 10.9 months vs 9.4 months for regorafenib (HR 0.80, p=0.0045). Grade ≥3 treatment-related adverse events occurred in 60% vs 37% with regorafenib, with five treatment-related deaths vs one in the regorafenib group.

• MOUNTAINEER (Tucatinib plus Trastuzumab) - Phase 2 trial in HER2+, RAS wild-type chemotherapy-refractory mCRC (n=84) demonstrated confirmed ORR of 39.3%, median duration of response 15.2 months, median PFS 8.1 months, and OS 23.9 months. Few patients discontinued due to adverse events with no treatment-emergent deaths.

• ARC-9 (Etrumadenant-Based Combination vs Regorafenib) - Phase 2 study in third-line mCRC (n=112) showed EZFB combination achieved median PFS of 6.2 vs 2.1 months (HR 0.27, p<0.0001) and OS of 19.7 vs 9.5 months (HR 0.37, p=0.0003) compared to regorafenib. Grade ≥3 treatment-emergent adverse events occurred in 82% vs 49% with regorafenib.

• ERBITAG (First-line Cetuximab) - Non-interventional study of RAS wild-type mCRC patients (n=728) receiving first-line cetuximab showed median PFS of 10.9 months, OS of 23.6 months, and ORR of 58.0%. Most common adverse event was acne-like rash (46.8% all grades, 4.7% grade 3-4).

• Anlotinib plus FTD-TPI - Single-arm phase 2 study in refractory mCRC (n=21) demonstrated ORR of 10.0%, disease control rate of 90.0%, and median PFS of 5.6 months. Most common grade ≥3 adverse events were neutropenia (25%) and thrombocytopenia (5%).

• NSABP FC-11 (Neratinib plus Cetuximab) - Phase 2 study in quadruple wild-type mCRC with prior oxaliplatin and irinotecan treatment (n=21) showed ORR/PFS at cycle 6 of 28% with intention-to-treat analysis. No grade 5 or unexpected adverse events were observed.

Kolupin's Place in the Evolving BRAF V600E mCRC Landscape

The treatment landscape for metastatic colorectal cancer has demonstrated substantial evolution over the past five years, with median overall survival showing marked improvement from 22.6 months for patients diagnosed between 2004-2012 to 32.4 months for those diagnosed 2016-2019. Five-year survival rates have similarly increased from 15.7% in 2004-2006 to 26% for patients diagnosed 2013-2015. These improvements are particularly notable for patients with BRAF-mutant and microsatellite unstable tumors, while surgical resection of liver metastases, immunotherapy utilization, and access to third-line treatments including regorafenib and trifluridine/tipiracil have emerged as key survival determinants.

The targeted therapy landscape has become increasingly sophisticated, with current guidelines recommending EGFR and VEGF inhibitors based on specific mutational profiles. Real-world evidence from over 9,000 patients demonstrates that 55.6% received VEGF inhibitors and 7.8% received EGFR inhibitors as first-line treatment, though more than one-third of patients received neither targeted therapy. Among patients with RAS wild-type tumors, EGFR inhibitor therapy demonstrated survival benefits, while VEGF inhibitors showed no survival advantage regardless of RAS status. Immunotherapy efficacy remains largely confined to MSI-high patients, representing a minority of cases, while the majority with microsatellite-stable disease continue to show primary resistance to immune checkpoint inhibitors.

Recent therapeutic advances include novel combinations and late-line options showing promising efficacy signals. Fruquintinib, a selective VEGFR1-3 inhibitor, has demonstrated significant progression-free survival and overall survival benefits in refractory disease, while combination strategies such as tislelizumab plus bevacizumab with chemotherapy have achieved response rates of 73.1% in MSS/RAS-mutant disease. Third-line treatment options have expanded with trifluridine/tipiracil plus bevacizumab combinations showing superior outcomes compared to standard late-line therapies, though response rates continue to decline with subsequent treatment lines, emphasizing the ongoing need for novel therapeutic approaches in treatment-refractory disease.

Key Design and Endpoints of CRDF-004 and Kolupin Trials

Recent clinical trials in metastatic colorectal cancer have employed diverse study designs across different treatment lines, ranging from large-scale phase 3 randomized controlled trials to network meta-analyses. These studies have established progression-free survival and overall survival as primary endpoints, with increasing focus on biomarker-driven patient stratification and novel statistical approaches for comparative effectiveness research.

Onvansertib's Broader Pipeline and Market Potential

Onvansertib is currently being investigated across multiple oncology indications beyond metastatic colorectal cancer, with varying stages of clinical and preclinical development. The most advanced trials include acute myeloid leukemia and small cell lung cancer, while several other tumor types show promising preclinical activity.

• Acute Myeloid Leukemia (AML) - Phase Ib study in relapsed/refractory patients using onvansertib (12-90 mg/m²) on days 1-5 combined with either low-dose cytarabine (20 mg/m²; days 1-10) or decitabine (20 mg/m²; days 1-5) in 28-day cycles. The decitabine combination achieved a maximum tolerated dose of 60 mg/m² and showed 24% complete remission rate in evaluable patients.

• Small Cell Lung Cancer (SCLC) - Currently in Phase II investigation for relapsed disease. Preclinical xenograft studies demonstrated superior tumor regression with daily oral administration at 60 mg/kg compared to intermittent dosing schedules (3 days on, 4 days off).

• Triple Negative Breast Cancer - Preclinical evaluation showed synergistic activity when combined with paclitaxel in SUM159 xenograft models, with significantly reduced tumor volume compared to paclitaxel monotherapy (p<0.0001).

• Ovarian Cancer - Demonstrated activity in both BRCA1-mutated and wild-type models, including patient-derived xenografts resistant to olaparib. The combination with olaparib showed tumor growth inhibition and improved survival, particularly in olaparib-resistant BRCA1-mutated settings.

• Endometrial Cancer - Preclinical studies in LKB1 p53 mouse models showed significant tumor growth reduction after 4 weeks of treatment, with synergistic effects when combined with paclitaxel.

• Uterine Serous Carcinoma - In vitro studies in ARK-1 and SPEC-2 cell lines demonstrated synergistic proliferation inhibition when combined with paclitaxel, inducing apoptosis and DNA damage.

Onvansertib's Promise in First-Line RAS-Mutated mCRC

The recent Phase II CRDF-004 trial results for onvansertib in RAS-mutated unresectable metastatic colorectal cancer (mCRC) mark a potentially transformative moment for patients facing this aggressive disease. By demonstrating a significantly improved objective response rate and an unreached median progression-free survival when added to standard first-line chemotherapy plus bevacizumab, onvansertib is carving out a strong case for its role in a patient population with limited targeted options.

This data reinforces the therapeutic potential of Polo-like kinase 1 (PLK1) inhibition, a mechanism that research indicates is particularly relevant in KRAS-mutant cancers. The strategic implications are clear: onvansertib could redefine the first-line treatment paradigm for RAS-mutated mCRC, moving beyond its previously explored second-line applications. This positions the drug to capture a significant market share by addressing a specific genetic subtype with a high unmet need, potentially establishing a new standard of care.

However, the path forward is not without considerations. While the safety profile has been manageable, the incidence of Grade 3/4 adverse events, particularly neutropenia, observed in earlier studies, will need careful attention in larger trials. Furthermore, existing evidence points to a significant reduction in efficacy for patients with prior bevacizumab exposure, suggesting that optimal sequencing and patient selection will be crucial for maximizing onvansertib's benefit. The transition to Phase III will be critical to confirm these promising early signals, provide robust long-term efficacy data, and solidify onvansertib's position as a valuable addition to the mCRC armamentarium.