Cardiff Oncology Presents Preclinical Data on its PLK1 Inhibitor Onvansertib in Combination with a HER2-Targeted ADC at the 2026 AACR Annual Meeting
Rhea-AI Summary
Cardiff Oncology (Nasdaq: CRDF) will present preclinical poster data at AACR 2026 showing its oral PLK1 inhibitor onvansertib potentiates trastuzumab deruxtecan (T-DXd) in HER2-low breast cancer models.
The combination produced tumor regression in nearly all mice, with complete responses up to 62%, synergistic cell‑kill in resistant lines, extended event‑free survival, and favorable tolerability. Poster available April 19, 2026; online after presentation.
AI-generated analysis. Not financial advice.
Positive
- Complete responses up to 62% in select HER2-low models
- Combination drove tumor regression in nearly all mice across resistant models
- Synergistic inhibition including fulvestrant- and CDK4/6i-resistant cell lines
- Extended event-free survival and improved tumor growth inhibition
- Favorable tolerability in vivo reported for the combination
Negative
- Data are preclinical only and not clinical efficacy in patients
- No clinical trial timing, human safety, or efficacy data disclosed
News Market Reaction – CRDF
On the day this news was published, CRDF declined 1.11%, reflecting a mild negative market reaction. Argus tracked a peak move of +3.4% during that session. Our momentum scanner triggered 9 alerts that day, indicating moderate trading interest and price volatility. This price movement removed approximately $1M from the company's valuation, bringing the market cap to $125.11M at that time.
Data tracked by StockTitan Argus on the day of publication.
Key Figures
Market Reality Check
Peers on Argus
CRDF was modestly down 0.59% as two oncology peers from the momentum set (e.g., NKTX, ONCY) also traded down (median move about -0.6%), suggesting broader biotech pressure rather than a company-specific move.
Historical Context
| Date | Event | Sentiment | Move | Catalyst |
|---|---|---|---|---|
| Apr 09 | Leadership appointments | Positive | -5.4% | CEO, CFO and COO appointments with option grants to support next growth phase. |
| Mar 20 | KOL webinar | Positive | -1.1% | Announcement of KOL webinar to discuss onvansertib data in first-line mCRC. |
| Mar 19 | AACR preclinical data | Positive | +0.6% | Planned AACR poster on onvansertib enhancing T-DXd activity in HER2-low models. |
| Feb 26 | Investor conferences | Neutral | -1.0% | Participation in three March investor conferences to engage the investment community. |
| Feb 24 | Earnings & Phase 2 | Positive | +12.3% | Full-year 2025 results and strong Phase 2 CRDF-004 efficacy and PFS data. |
Recent history shows limited or negative reactions to non-financial news, with a stronger positive move only on the full-year 2025/Phase 2 data update.
Over the last few months, Cardiff Oncology has focused on advancing onvansertib and reshaping leadership. A February 24, 2026 earnings and Phase 2 update highlighted a confirmed ORR of 72.2% vs 43.2% for standard care and cash of $58.3M, driving a 12.35% gain. Subsequent conference and webinar announcements, plus leadership changes in early April 2026, saw mild to negative reactions. The current AACR preclinical combination data fits into this ongoing R&D narrative around onvansertib.
Market Pulse Summary
This announcement details preclinical results showing onvansertib plus trastuzumab deruxtecan driving tumor regression and complete responses up to 62% in HER2-low breast cancer models, with extended event-free survival and in vivo tolerability. It builds on earlier AACR-related communications and broader clinical progress in colorectal cancer. Investors may track future updates on translational plans, additional efficacy metrics, and how these combination data integrate with Cardiff’s ongoing registrational strategy for onvansertib.
Key Terms
plk1 inhibitor medical
her2-low medical
antibody-drug conjugate medical
trastuzumab deruxtecan medical
adc medical
apoptosis medical
triple-negative breast cancer medical
event-free survival medical
AI-generated analysis. Not financial advice.
Onvansertib in combination with trastuzumab deruxtecan demonstrated enhanced antitumor activity, including tumor regression and apoptosis in HER2-low breast cancer models, supporting its potential for patients with limited treatment options
SAN DIEGO, Calif., April 17, 2026 (GLOBE NEWSWIRE) -- Cardiff Oncology, Inc. (Nasdaq: CRDF), a clinical-stage biotechnology company leveraging PLK1 inhibition to develop novel therapies across a range of cancers, will present new preclinical data in a poster at the American Association for Cancer Research (AACR) Annual Meeting 2026, taking place April 17–22 in San Diego, California. These data highlight the potential of Cardiff’s highly specific oral PLK1 inhibitor, onvansertib, in combination with the HER2-targeted antibody-drug conjugate (ADC), trastuzumab deruxtecan (T-DXd), demonstrating robust antitumor activity and the ability to overcome resistance in HER2-low breast cancer models.
“These preclinical findings highlight a potential new opportunity for onvansertib, demonstrating its ability to enhance the activity of ADCs, which are becoming mainstays in oncology across multiple indications,” said Tod Smeal, Ph.D., Chief Scientific Officer of Cardiff Oncology. “By enhancing and prolonging DNA damage, this combination appears to drive greater apoptosis than either agent alone, offering a promising new approach for patients whose cancers have become resistant to standard-of-care treatments.”
Poster Presentation Highlights:
- Onvansertib + T-DXd synergistically inhibited the viability of HER2-low breast cancer cell lines, including fulvestrant- and CDK4/6i-resistant cells
- In the resistant triple-negative breast cancer model and two hormone receptor-positive models, the combination drove tumor regression in nearly all mice, with complete response rates up to
62% - Increased tumor regression, improved tumor growth inhibition, and extended event-free survival across models
- Combination showed favorable tolerability in vivo
Following the presentation on April 19, 2026 from 2:00–5:00 PM PT, the poster titled “PLK1 inhibitor onvansertib potentiates the antitumor efficacy of trastuzumab deruxtecan (T-DXd) and reverses its resistance in therapy-resistant HER2-low breast cancer models” will be available on the Scientific Publications page of the Company's website.
About Onvansertib
Onvansertib is a highly specific, oral PLK1 inhibitor currently in mid-stage clinical development for RAS-mutated metastatic colorectal cancer. It is also being evaluated in multiple other cancers through investigator-initiated studies, including metastatic pancreatic ductal adenocarcinoma (mPDAC), small cell lung cancer (SCLC), triple-negative breast cancer (TNBC), and chronic myelomonocytic leukemia (CMML).
About Cardiff Oncology, Inc.
Cardiff Oncology is a clinical-stage biotechnology company advancing innovative cancer treatments focused on PLK1 inhibition, a validated oncology target with practice-changing potential. Our lead asset, onvansertib, is a highly specific, oral PLK1 inhibitor currently being evaluated in a Phase 2 trial for first-line treatment of RAS-mutated metastatic colorectal cancer (mCRC), addressing a large, underserved patient population with high unmet need. Onvansertib is also under investigation in other PLK1-driven cancers through ongoing investigator-initiated trials and has shown robust single agent clinical activity in hard-to-treat tumors. By targeting tumor vulnerabilities, we aim to overcome treatment resistance and deliver improved clinical outcomes for patients.
For more information, please visit https://www.cardiffoncology.com.
Forward-Looking Statements
Certain statements in this press release are forward-looking within the meaning of the Private Securities Litigation Reform Act of 1995. These statements may be identified using words such as "anticipate," "believe," "forecast," "estimated" and "intend" or other similar terms or expressions that concern Cardiff Oncology's expectations, strategy, plans or intentions. These forward-looking statements are based on Cardiff Oncology's current expectations and actual results could differ materially. There are several factors that could cause actual events to differ materially from those indicated by such forward-looking statements. These factors include, but are not limited to, clinical trials involve a lengthy and expensive process with an uncertain outcome, and results of earlier studies and trials may not be predictive of future trial results; our clinical trials may be suspended or discontinued due to unexpected side effects or other safety risks that could preclude approval of our product candidate; results of preclinical studies or clinical trials for our product candidate could be unfavorable or delayed; our need for additional financing; risks related to business interruptions, including the outbreak of COVID-19 coronavirus and cyber-attacks on our information technology infrastructure, which could seriously harm our financial condition and increase our costs and expenses; uncertainties of government or third party payer reimbursement; dependence on key personnel; limited experience in marketing and sales; substantial competition; uncertainties of patent protection and litigation; dependence upon third parties; and risks related to failure to obtain FDA clearances or approvals and noncompliance with FDA regulations. There are no guarantees that our product candidate will be utilized or prove to be commercially successful. Additionally, there are no guarantees that future clinical trials will be completed or successful or that our product candidate will receive regulatory approval for any indication or prove to be commercially successful. Investors should read the risk factors set forth in Cardiff Oncology's Form 10-K for the year ended December 31, 2025, and other periodic reports filed with the Securities and Exchange Commission. While the list of factors presented here is considered representative, no such list should be considered to be a complete statement of all potential risks and uncertainties. Unlisted factors may present significant additional obstacles to the realization of forward-looking statements. Forward-looking statements included herein are made as of the date hereof, and Cardiff Oncology does not undertake any obligation to update publicly such statements to reflect subsequent events or circumstances.
Investor Contact:
Candice Masse
astr partners
candice.masse@astrpartners.com
Media Contact:
Amy Bonanno
Lyra Strategic Advisory
abonanno@lyraadvisory.com
