Alirocumab Plus Cemiplimab in Immunorefractory NSCLC: A Single Arm Phase 2 Study.

Technical Summary: Alirocumab Plus Cemiplimab in Immunorefractory NSCLC

Problem Statement
Despite the revolutionary impact of immune checkpoint inhibitors (ICIs) on non-small cell lung cancer (NSCLC) treatment, a significant majority of patients with metastatic disease experience primary or secondary resistance. For patients progressing after first-line chemo-immunotherapy, standard-of-care options (e.g., docetaxel with or without ramucirumab) offer limited efficacy, with response rates of 7–20% and median overall survival (OS) of 7.5–10 months. There is a critical unmet need for safe, effective strategies to overcome immunotherapy resistance. Preclinical evidence suggests that Proprotein convertase subtilisin/kexin type 9 (PCSK9), traditionally known for cholesterol metabolism, acts as an inhibitory immunoregulator within the tumor microenvironment, promoting immune evasion through mechanisms such as MHC I degradation and increased myeloid-derived suppressor cells (MDSCs). While retrospective data hinted at improved survival in cancer patients taking PCSK9 inhibitors for cholesterol management, the prospective clinical efficacy of PCSK9 inhibition to reverse immunotherapy resistance in NSCLC had not been established.

Methodology
The authors conducted a multi-center, open-label, single-arm Phase II study (TOP 2201) to evaluate the combination of alirocumab (an anti-PCSK9 monoclonal antibody) and cemiplimab (an anti-PD1 antibody) in patients with metastatic NSCLC who had progressed on prior immune checkpoint blockade.

• Study Design: The trial utilized a two-stage design. Stage 1 was a safety lead-in cohort of 15 patients. Stage 2 was an expansion cohort. The primary endpoint was the Objective Response Rate (ORR) per RECIST v1.1. Secondary endpoints included Progression-Free Survival (PFS), Overall Survival (OS), Duration of Response (DOR), Disease Control Rate (DCR), and safety.
• Patient Population: 60 patients were enrolled between May 2023 and September 2025. All patients had metastatic NSCLC with disease progression on prior anti-PD-1/PD-L1 therapy (alone or in combination with chemotherapy/anti-VEGF).
• Treatment Regimen: Patients received cemiplimab 350 mg IV every 3 weeks and alirocumab 150 mg subcutaneously every 2 weeks.
• Translational Analysis: The study incorporated extensive biomarker analysis, including Next-Generation Sequencing (NGS) of tumor samples (available for 56/58 evaluable patients) to identify genomic alterations. Exploratory analyses correlated clinical outcomes with alterations in the PIK3CA/PTEN/AKT1 axis.
• Preclinical Validation: The study included in vitro experiments using human NSCLC cell lines (H596, H226, H1703) and normal lung epithelial cells (BEAS-2B, BCi-NS1.1). These experiments involved pharmacologic inhibition (alpelisib, capivasertib) and genetic manipulation (CRISPR knockout, siRNA knockdown) of PIK3CA, AKT1, and PTEN to assess their impact on PCSK9 secretion and expression. Bioinformatic analyses were performed on The Cancer Genome Atlas (TCGA) LUAD and LUSC cohorts to correlate gene expression and copy number variations with PCSK9 and SREBF1 levels.

Key Results

• Overall Efficacy: In the evaluable population (n=58), the ORR was 14.78% (90% CI, 5.30–25.43). The median PFS was 2.5 months (95% CI, 1.5–3.0), and the median OS was 7.3 months (95% CI, 5.4–12.3). The Disease Control Rate (DCR) was 58.6%.
• Safety: The combination was well-tolerated. The most common treatment-related adverse events (TRAEs) were anemia (22%) and fatigue. Grade 3 TRAEs occurred in 12% of patients (anemia, Guillain-Barre Syndrome, elevated amino transferase). There were no Grade 4 or higher TRAEs and no treatment-related deaths.
• Biomarker Discovery: A distinct molecular subset was identified. All objective responders (n=5) harbored alterations in the PI3K pathway, specifically in PIK3CA, PTEN, or AKT1.
  • Stratified Efficacy: In the cohort with PIK3CA, PTEN, or AKT1 alterations (n=17), the ORR was 29.4% (5/17). In contrast, no objective responses were observed in patients without these alterations (0/39). The association between these alterations and response was statistically significant (p=0.0032, Fisher's exact test).
  • Survival: Patients with these alterations had a median OS of 13.64 months compared to 7.2 months in the unaltered group.
• Mechanistic Insights:
  • TCGA Analysis: In lung squamous cell carcinoma (LUSC) cohorts, AKT1 and PIK3CA expression (or gain-of-function mutations) positively correlated with PCSK9 and SREBF1 (encoding SREBP1) expression. Conversely, PTEN loss of function correlated with increased PCSK9 expression.
  • In Vitro Validation: Pharmacologic inhibition of PIK3CA (alpelisib) and AKT1 (capivasertib) decreased tumor cell-secreted PCSK9. Conversely, PTEN knockdown (via siRNA or CRISPR) increased PCSK9 secretion. This supports a model where oncogenic activation of the PI3K/AKT pathway or loss of PTEN upregulates PCSK9 via SREBP1, driving immune evasion.
  • LDL-C Correlation: Within the altered cohort, patients who achieved an objective response showed a significantly greater reduction in LDL-C at 6 weeks compared to non-responders, suggesting a link between the drug's metabolic effect and anti-tumor activity.

Significance and Claims
The paper claims to provide the first clinical proof-of-principle that PCSK9 inhibition can overcome immunotherapy resistance in a specific subset of NSCLC patients. The study identifies PIK3CA, PTEN, and AKT1 alterations as potential biomarkers of response, with the combination therapy yielding a clinically meaningful ORR of approximately 30% in this molecularly defined group.

The authors posit that these genomic alterations drive intratumoral PCSK9 expression via the SREBP1 axis, creating an immunosuppressive microenvironment that is reversible by alirocumab. While the overall population results were modest, the significant enrichment of responders in the PIK3CA/PTEN/AKT1 altered group suggests a targeted therapeutic strategy. The authors conclude that these findings warrant further investigation in larger, confirmatory studies to validate PIK3CA/PTEN/AKT1 status as a selection criterion for anti-PCSK9 based combination therapies in immunorefractory NSCLC. The paper explicitly notes limitations, including the small sample size and the fact that approximately 20% of non-responders also possessed these alterations, indicating that other regulatory mechanisms may be at play.