HER2-low expression in patients with advanced or metastatic solid tumors

BACKGROUND

Human epidermal growth factor receptor 2 (HER2)-low is a newly defined category with HER2 1+ or 2+ expression by immunohistochemistry (IHC) and lack of HER2 gene amplification measured by in situ hybridization (ISH). Much remains unknown about the HER2-low status across tumor types and changes in HER2 status between primary and metastatic samples.

PATIENTS AND METHODS

HER2 expression by IHC was evaluated in 4701 patients with solid tumors. We have evaluated the HER2 expression by IHC and amplification by ISH in paired breast and gastric/gastroesophageal (GEJ) primary and metastatic samples. HER2 expression was correlated with ERBB2 genomic alterations evaluated by next-generation sequencing (NGS) in non-breast, non-gastric/GEJ samples.

RESULTS

HER2 expression (HER2 IHC 1-3+) was found in half (49.8%) of the cancers, with HER2-low (1 or 2+) found in many tumor types: 47.1% in breast, 34.6% in gastric/GEJ, 50.0% in salivary gland, 46.9% in lung, 46.5% in endometrial, 46% in urothelial, and 45.5% of gallbladder cancers. The concordance evaluation of HER2 expression between primary and metastatic breast cancer samples showed that HER2 3+ remained unchanged in 87.1% with a strong agreement between primary and metastatic samples, with a weighted kappa (Κ) of 0.85 (95% confidence interval 0.79-0.91). ERBB2 alterations were identified in 117 (7.5%) patients with non-breast, non-gastric/GEJ solid tumors who had NGS testing. Of 1436 patients without ERBB2 alterations, 512 (35.7%) showed any level HER2 expression by IHC.

CONCLUSION

Our results show that HER2-low expression is frequently found across tumor types. These findings suggest that many patients with HER2-low solid tumors might benefit from HER2-targeted therapies.

Phase Ib study of eprenetapopt (APR-246) in combination with pembrolizumab in patients with advanced or metastatic solid tumors

Background

We conducted a phase I, multicenter, open-label, dose-finding, and expansion study to determine the safety and preliminary efficacy of eprenetapopt (APR-246) combined with pembrolizumab in patients with advanced/metastatic solid tumors (ClinicalTrials.gov NCT04383938).

Patients and methods

For dose-finding, requirements were non-central nervous system primary solid tumor, intolerant to/progressed after ≥1 line of treatment, and eligible for pembrolizumab; for expansion: (i) gastric/gastroesophageal junction tumor, intolerant to/progressed after first-line treatment, and no prior anti-programmed cell death receptor-1 (PD-1)/programmed death-ligand 1 (PD-L1) therapy; (ii) bladder/urothelial tumor, intolerant to/progressed after first-line cisplatin-based chemotherapy, and no prior anti-PD-1/PD-L1 therapy; (iii) non-small-cell lung cancer (NSCLC) with previous anti-PD-1/PD-L1 therapy. Patients received eprenetapopt 4.5 g/day intravenously (IV) on days 1-4 with pembrolizumab 200 mg IV on day 3 in each 21-day cycle. Primary endpoints were dose-limiting toxicity (DLT), adverse events (AEs), and recommended phase II dose (RP2D) of eprenetapopt.

Results

Forty patients were enrolled (median age 66 years; range 27-85) and 37 received eprenetapopt plus pembrolizumab. No DLTs were reported and the RP2D for eprenetapopt in combination was 4.5 g/day IV on days 1-4. The most common eprenetapopt-related AEs were dizziness (35.1%), nausea (32.4%), and vomiting (29.7%). AEs leading to eprenetapopt discontinuation occurred in 2/37 patients (5.4%). In efficacy-assessable patients (n = 29), one achieved complete response (urothelial cancer), two achieved partial responses (NSCLC, urothelial cancer), and six patients had stable disease.

Conclusions

The eprenetapopt plus pembrolizumab combination was well tolerated with an acceptable safety profile and showed clinical activity in patients with solid tumors.

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Eprenetapopt in combination with pembrolizumab was well tolerated with an acceptable safety profile.

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Eprenetapopt plus pembrolizumab demonstrated clinical activity in heavily pre-treated patients with solid tumors.

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This is the first clinical trial evaluating the combination of a p53 reactivator with immuno-oncology therapy.

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This work informs the development of treatment combining immunotherapy with agents targeting specific pathways such as p53.

PIK3CA mutations in plasma circulating tumor DNA predict survival and treatment outcomes in patients with advanced cancers

Background

Oncogenic mutations in PIK3CA are prevalent in diverse cancers and can be targeted with inhibitors of the phosphoinositide-3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/AKT/mTOR) pathway. Analysis of circulating tumor DNA (ctDNA) provides a minimally invasive approach to detect clinically actionable PIK3CA mutations.

Patients and methods

We analyzed PIK3CA hotspot mutation frequency by droplet digital PCR (QX 200; BioRad) using 16 ng of unamplified plasma-derived cell-free DNA from 68 patients with advanced solid tumors (breast cancer, n = 41; colorectal cancer, n = 13; other tumor types, n = 14). Results quantified as variant allele frequencies (VAFs) were compared with previous testing of archival tumor tissue and with patient outcomes.

Results

Of 68 patients, 58 (85%) had PIK3CA mutations in tumor tissue and 43 (74%) PIK3CA mutations in ctDNA with an overall concordance of 72% (49/68, κ = 0.38). In a subset analysis, which excluded samples from 26 patients known not to have disease progression at the time of sample collection, we found an overall concordance of 91% (38/42; κ = 0.74). PIK3CA-mutated ctDNA VAF of ≤8.5% (5% trimmed mean) showed a longer median survival compared with patients with a higher VAF (15.9 versus 9.4 months; 95% confidence interval 6.7-17.1 months; P = 0.014). Longitudinal analysis of ctDNA in 18 patients with serial plasma collections (range 2-22 time points, median 5) showed that those with a decrease in PIK3CA VAF had a longer time to treatment failure (TTF) compared with patients with an increase or no change (10.7 versus 2.6 months; P = 0.048).

Conclusions

Detection of PIK3CA mutations in ctDNA is concordant with testing of archival tumor tissue. Low quantity of PIK3CA-mutant ctDNA is associated with longer survival and a decrease in PIK3CA-mutant ctDNA on therapy is associated with longer TTF.

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Testing for PIK3CA mutations in ctDNA is concordant with testing of tumor tissue.

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High PIK3CA-mutant abundance in ctDNA was associated with shorter survival.

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Increasing PIK3CA-mutant abundance in serial blood samples was associated with shorter TTF.

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Longitudinal monitoring of PIK3CA-mutant ctDNA tracked with cancer clinical course.