Search

KRAS is one of the most commonly mutated oncogenes in lung, colorectal, and pancreatic cancers. Recent clinical trials directly targeting KRAS G12C presented encouraging results for a large population of non-small cell lung cancer (NSCLC), but resistance to treatment is a concern. Continued exploration of new inhibitors and preclinical models is needed to address resistance mechanisms and improve duration of patient responses. To further enable the development of KRAS G12C inhibitors, we present a preclinical framework involving translational, non-invasive imaging modalities (CT and PET) and histopathology in a conventional xenograft model and a novel KRAS G12C knock-in mouse model of NSCLC. We utilized an in-house developed KRAS G12C inhibitor (Compound A) as a tool to demonstrate the value of this framework in studying in vivo pharmacokinetic/pharmacodynamic (PK/PD) relationship and anti-tumor efficacy. We characterized the Kras G12C-driven genetically engineered mouse model (GEMM) and identify tumor growth and signaling differences compared to its Kras G12D-driven counterpart. We also find that Compound A has comparable efficacy to sotorasib in the Kras G12C-driven lung tumors arising in the GEMM, but like observations in the clinic, some tumors inevitably progress on treatment. These findings establish a foundation for evaluating future KRAS G12C inhibitors that is not limited to xenograft studies and can be applied in a translationally relevant mouse model that mirrors human disease progression and resistance.

PDF file - 123K

Anti-programmed death 1 (PD-1) monoclonal antibodies improve the survival of metastatic melanoma patients. Predictive or monitoring biomarkers for response to this therapy could improve the clinical management of these patients. To date, no established biomarkers are available for monitoring the response to immunotherapy. Tumor- specific mutations in circulating tumor DNA (ctDNA) such as BRAF and NRAS mutations for melanoma patients have been proposed for monitoring of immunotherapy response. We present seven illustrative cases for the use of ctDNA BRAF and NRAS mutations' monitoring in plasma. The cases described exemplify four distinct clinical benefit patterns: rapid and durable complete response (CR), early progression, followed by CR, CR followed by early progression after interrupting treatment and long-term disease stabilization. These representative cases suggest that comprehensive BRAF/NRAS ctDNA monitoring during anti-PD1 therapy is informative and can be of added value for the monitoring of melanoma patients gaining clinical benefit on anti-PD1 treatment. An important advantage of our approach is that using the cartridge system on the Idylla platform for mutation analysis, the results become available the same day 2 h after plasma collection. Therefore, in the future, the ctDNA level can be an element in the clinical management of the patients.

Monoclonal antibodies that block the programmed death-1 (anti-PD-1) or cytotoxic T-lymphocyte antigen-4 (CTLA-4) immune checkpoint receptors (pembrolizumab, nivolumab, ipilimumab, or the combination of nivolumab with ipilimumab) are approved treatment option for patients with advanced melanoma. Over half of all patients are refractory to these immunotherapies and are in need of alternative or complementary treatment options. Talimogene laherparepvec (T-VEC) is a first-in-class intralesionally delivered oncolytic immunotherapy, which has proven efficacy in the treatment of advanced melanoma. A proportion of patients treated with T-VEC will benefit from an abscopal response of noninjected metastases indicative of a systemic antitumor immune response elicited by the intratumoral injections. At present it remains unknown whether the systemic antitumor responses elicited by T-VEC are nonredundant with immune-checkpoint blockade. Recent data on potential synergy between T-VEC and both PD-1 and CTLA-4 blockade suggest that the mechanism of action may be complementary. We report on the successful treatment with intralesional T-VEC of two female patients with locoregionally advanced BRAF V600 wild-type melanoma who previously progressed on anti-PD-1 and anti-CTLA-4 inhibitors.

Summary Background Patients with BRAF V600 -mutant melanoma benefit from treatment with the combination of BRAF and MEK inhibitors, but resistance and disease progression develops in most patients. Preclinical studies and case studies have indicated that acquired resistance to BRAF inhibition can be reversible. We aimed to assess the anti-tumour activity of rechallenge with BRAF plus MEK inhibition in a prospective clinical trial. Methods In this open-label, single arm, dual-centre, phase 2 academic study in Belgium, patients aged 18 years or older with BRAF V600 -mutant melanoma who had previously progressed on BRAF inhibitors (with or without MEK inhibitors) and were off-treatment for at least 12 weeks, were treated with dabrafenib 150 mg orally twice per day plus trametinib 2 mg orally once per day. The primary endpoint was the proportion of patients with investigator-assessed overall response at any time (defined as complete response or partial response according to Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 confirmed on two occasions, at least 28 days after the first response was recorded). Analyses were done in the intention-to-treat population. The study is ongoing but no longer recruiting patients. This trial is registered with ClinicalTrials.gov, number NCT02296996. Findings Between April 5, 2014, and Feb 2, 2016, 25 patients were enrolled and initiated treatment in our study. A partial response was documented in eight (32%) of 25 patients (95% CI 15–54; six patients had progressed on previous treatment with dabrafenib plus trametinib and two patients had progressed on previous BRAF inhibitor monotherapy). Stable disease was noted in ten patients (40%; 95% CI 21–61). Rechallenge with dabrafenib plus trametinib was well tolerated. There were no unexpected or grade 4 or 5 treatment-related adverse events. Grade 3 adverse events occurred in two patients (8%; panniculitis [n=1] and pyrexia [n=1]). Serious adverse events which occurred on study were one patient with an Addison crisis triggered by grade 2 pyrexia symptoms that resolved after discontinuation of dabrafenib and trametinib. No patients died as a result of study treatment. Interpretation Rechallenge with dabrafenib plus trametinib showed anti-tumour activity in patients who had previously progressed on BRAF inhibitors and as such, rechallenge represents a potential new treatment option for these patients. Funding Vlaamse Liga Tegen Kanker, Novartis.

Mutant epidermal growth factor receptor (EGFR) is a major driver of non-small-cell lung cancer (NSCLC). Marketed first generation inhibitors, such as erlotinib, effect a transient beneficial response in EGFR mutant NSCLC patients before resistance mechanisms render these inhibitors ineffective. Secondary oncogenic EGFR mutations account for approximately 50% of relapses, the most common being the gatekeeper T790M substitution that renders existing therapies ineffective. The discovery of PF-06459988 (1), an irreversible pyrrolopyrimidine inhibitor of EGFR T790M mutants, was recently disclosed.1 Herein, we describe our continued efforts to achieve potency across EGFR oncogenic mutations and improved kinome selectivity, resulting in the discovery of clinical candidate PF-06747775 (21), which provides potent EGFR activity against the four common mutants (exon 19 deletion (Del), L858R, and double mutants T790M/L858R and T790M/Del), selectivity over wild-type EGFR, and desirable ADME properties. Compound 21 is currently being evaluated in phase-I clinical trials of mutant EGFR driven NSCLC.

First generation EGFR TKIs (gefitinib, erlotinib) provide significant clinical benefit for NSCLC cancer patients with oncogenic EGFR mutations. Ultimately, these patients' disease progresses, often driven by a second-site mutation in the EGFR kinase domain (T790M). Another liability of the first generation drugs is severe adverse events driven by inhibition of WT EGFR. As such, our goal was to develop a highly potent irreversible inhibitor with the largest selectivity ratio between the drug-resistant double mutants (L858R/T790M, Del/T790M) and WT EGFR. A unique approach to develop covalent inhibitors, optimization of reversible binding affinity, served as a cornerstone of this effort. PF-06459988 was discovered as a novel, third generation irreversible inhibitor, which demonstrates (i) high potency and specificity to the T790M-containing double mutant EGFRs, (ii) minimal intrinsic chemical reactivity of the electrophilic warhead, (iii) greatly reduced proteome reactivity relative to earlier irreversible EGFR inhibitors, and (iv) minimal activity against WT EGFR.