BeyondSpring Inc. has published compelling clinical data demonstrating that its investigational drug Plinabulin can overcome checkpoint inhibitor resistance through a novel dendritic cell maturation mechanism. The Phase 1 study, published in Med (Cell Press), showed that combining Plinabulin with radiation and PD-1 inhibitors achieved meaningful responses in heavily pretreated patients across multiple cancer types.
Clinical Efficacy in Checkpoint Inhibitor-Resistant Patients
The investigator-initiated Phase 1 translational trial (NCT04902040) evaluated 19 patients with eight different cancer types who had failed prior immune checkpoint inhibitor (ICI) therapy. Among 13 evaluable patients, the triple combination achieved an overall response rate (ORR) of 23% and a disease control rate (DCR) of 54% in non-irradiated lesions.
The most striking results were observed in specific cancer types. Non-small cell lung cancer (NSCLC) patients showed a 100% response rate (2/2), head and neck squamous cell carcinoma (HNSCC) patients achieved a 67% response rate (2/3), and both Hodgkin lymphoma patients (2/2) responded to treatment. Notably, both Hodgkin lymphoma patients maintained durable responses exceeding 19 months despite having received 12-16 prior lines of therapy.
"These results offer early but important signals that Plinabulin's dendritic cell maturation mechanism could play a pivotal role in reversing ICI-acquired resistance," said Dr. Steven Lin, M.D., Ph.D., corresponding author and Professor of Radiation Oncology at The University of Texas MD Anderson Cancer Center. "The ability of Plinabulin to activate the immune system in this setting is both scientifically intriguing and clinically promising—particularly given the durability of responses in some heavily pretreated patients."
Mechanism of Action and Biomarker Discovery
The study confirmed Plinabulin's unique mechanism of action through GEF-H1 signaling. Flow cytometry analysis of whole blood revealed increased expression of dendritic cell maturation markers (CCR7, CD80, CD83) and a shift in monocyte subpopulations from classical to proinflammatory phenotype in responding patients.
Single-cell RNA sequencing successfully differentiated responders from non-responders and identified baseline GEF-H1 immune gene expression as a potential predictive biomarker for Plinabulin response. This discovery could enable patient pre-selection and clinical response prediction, potentially improving treatment outcomes.
Plinabulin functions as a first-in-class dendritic cell maturation agent that binds reversibly to a unique site on tubulin, destabilizing microtubules in a controlled manner to release GEF-H1. The immune protein GEF-H1 then activates the RhoA/ROCK signaling pathway, promoting dendritic cell maturation and anti-tumor T-cell immunity.
Treatment Regimen and Study Design
The open-label, single-arm Phase 1 basket study at MD Anderson Cancer Center investigated the safety and efficacy of the triple combination in patients refractory or relapsed after prior immunotherapy. The treatment regimen included:
- Radiation: Local consolidative RT (8 Gy × 3; 12.5 Gy × 4; or 4 Gy × 5) administered only during the first cycle
- Plinabulin: 30 mg/m² on Days 1 and 4 of Cycle 1 (3-6 hours post-RT); Day 1 of Cycle 2 onward
- PD-1 inhibitor: Pembrolizumab 200 mg every 21 days or nivolumab 240 mg every 14 days
Among the 19 patients treated, 14 received pembrolizumab and 5 received nivolumab. The primary endpoint was investigator-assessed ORR (RECIST 1.1) in non-irradiated lesions, with disease control rate as a secondary endpoint.
Broader Clinical Development Program
The current findings build upon Plinabulin's established clinical track record across multiple studies involving approximately 800 patients. The drug has demonstrated durable anti-cancer activity and a favorable safety profile while significantly reducing chemotherapy-induced neutropenia.
Previous clinical milestones include a Phase 3 trial in second and third-line NSCLC (Dublin-3, n=559) where Plinabulin plus docetaxel demonstrated a significant overall survival benefit over standard-of-care docetaxel. Additionally, a Phase 2 study combining Plinabulin with pembrolizumab and docetaxel in patients who progressed on PD-1/L1 inhibitors (n=47) achieved a median progression-free survival of 6.8 months and a 15-month overall survival rate of 78%.
"This study builds upon the seminal work of Nobel Laureate Dr. Ralph Steinman and Dr. Ira Mellman, who helped define the essential role of dendritic cells in immune activation," said Lan Huang, Ph.D., Co-Founder, Chairman, and CEO of BeyondSpring. "Plinabulin's ability to drive dendritic cell maturation and induce immune responsiveness offers a potential breakthrough strategy for patients who are refractory or relapsed on checkpoint inhibitors."
