Olaratumab: PDGFR-α inhibition as a novel tool in the treatment of advanced soft tissue sarcomas

An image-based Abplex method for high-throughput GPCRs antibody discovery

As the field of antibody therapeutics advances rapidly, membrane proteins, particularly G protein-coupled receptors (GPCRs), have emerged as highly sought-after drug targets. However, the challenges associated with extracting membrane proteins have created a demand for effective antibody screening systems targeting these proteins. In this study, we propose developing an innovative antibody screening strategy (Abplex) based on high-content imaging. This approach leverages intact cells that express target membrane proteins, facilitating the presentation of proteins in their native conformation. Furthermore, it acquires both specific and non-specific binding signals in a single well, thereby bolstering the robustness of the outcomes. The technique involves just one step and can be completed within 50 min, enabling the analysis of a single sample in just one second. The amalgamation of dependable experimental findings, a simplified workflow, reduced hands-on time, and a swift analytical pace positions our method for superior throughput and precision when juxtaposed with traditional techniques such as CbELISA and FACS. Moreover, we introduce the concept of cell barcoding, wherein cells are labeled with different fluorescence spatial patterns. This feature allows for multiplexed detection to meet the needs of various experiments. The characteristics of Abplex promise to expedite GPCR-targeting antibody discovery, advance therapeutics and enable new disease treatments.

Combination therapy with Olaratumab/doxorubicin in advanced or metastatic soft tissue sarcoma -a single-Centre experience

Background

The antibody targeting platelet-derived growth factor receptor alpha (PDGFRA), olaratumab, was approved in 2016 for metastatic soft tissue sarcoma (STS) in combination with doxorubicin based on promising results of a phase Ib/II trial by the Food and Drug Administration (FDA). However, recently the phase III ANNOUNCE trial could not confirm the additional value of olaratumab in this context.

Methods

Here, in a retrospective analysis we share our single-centre experience with olaratumab/doxorubicin in STS by including n = 32 patients treated with olaratumab/doxorubicin between 2016 and 2019.

Results

Median progression-free survival (PFS) in the overall cohort was 3.1 months (range 0.6–16.2). A response [complete remission (CR), partial remission (PR) or stable disease (SD)] was seen in n = 11 (34%) cases, whereas n = 21 (66%) patients showed progressive disease (PD). In n = 9 patients surgery was performed subsequently in an individual therapeutic approach. Out of n = 5 patients receiving additional regional hyperthermia, n = 3 achieved PR or SD.

Conclusions

This single-centre experience does also not support the promising phase Ib/II results for olaratumab/doxorubicin in STS. However, our findings do not preclude that olaratumab combination therapy could be valuable in a neoadjuvant setting. This warrants further exploration also taking into account the heterogeneous nature of STS.

Olaratumab administered in two cases of phyllodes tumour of the breast: end of the beginning?

Phyllodes tumours of the breast are rare mesenchymal tumours with differential malignant potential. Treatment of choice is radical excision with negative margins. Radiation therapy has shown controversial results in small series. Chemotherapy in the adjuvant setting still remains a matter of debate. Doxorubicin-based chemotherapy is recommended for breast sarcomas' first-line treatment. Herein we present two cases of breast phyllodes tumour treated with the recent combination of doxorubicin and olaratumab.

Olaratumab combined with doxorubicin and ifosfamide overcomes individual doxorubicin and olaratumab resistance of an undifferentiated soft-tissue sarcoma in a PDOX mouse model

Olaratumab (OLA), a monoclonal antibody against platelet-derived growth factor receptor alpha (PDGFRα), has recently been used against soft-tissue sarcoma (STS) combined with doxorubicin (DOX), with limited efficacy. The goal of the present study was to determine the efficacy of OLA in combination with DOX and ifosfamide (IFO) on STS. Undifferentiated soft-tissue sarcoma (USTS) from a striated muscle of a patient was grown orthotopically in the right biceps femoris muscle of nude mice to establish USTS patient-derived orthotopic xenograft (PDOX) model. USTS PDOX tumors were treated with OLA alone, DOX alone, DOX combined with IFO, OLA combined with DOX or IFO, and OLA combined with DOX and IFO. Tumor size and body weight were measured during the 14 days of treatment. Tumor growth was arrested by OLA combined with DOX and IFO. Tumors treated with OLA combined with DOX and IFO had the most necrosis. The present study demonstrates the power of the PDOX model to identify the novel effective treatment strategy of the combination of OLA, DOX and IFO for soft-tissue sarcomas.

Investigating a chimeric anti-mouse PDGFRα antibody as a radiosensitizer in primary mouse sarcomas

BACKGROUND

Olaratumab (LY3012207/IMC-3G3/Lartruvo™) is a fully human monoclonal antibody specific for platelet-derived growth factor receptor alpha (PDGFRα). Phase Ib/II trial results of olaratumab plus doxorubicin in adult patients with advanced soft tissue sarcoma (STS) supported accelerated FDA approval of this regimen. Radiation therapy (RT) is frequently used for high-risk localized STS. However, olaratumab has not been tested with concurrent RT. Here, we evaluate the chimeric anti-mouse PDGFRα antibody 1E10Fc as a radiosensitizer in a primary mouse model of STS.

METHODS

Primary STS were initiated in mice. When tumors reached 70 mm³, mice were allocated into treatment groups: 1) isotype, 2) 1E10Fc, 3) isotype + RT, 4) 1E10Fc + RT. 1E10Fc or isotype was given biweekly. RT (25 Gy delivered in 5 daily 5 Gy fractions) was initiated on Day 0 with first drug treatment. Tumors were measured 3× per week. Upon reaching 900 mm³, tumors and lungs were harvested. A two-way ANOVA was performed to compare tumor growth delay. Primary tumors were stained for CD31 and PDGFRα and lungs were assessed for micrometastases. A Chi-square test was performed to compare the development of micrometastases in the lungs after treatment with 1E10Fc or isotype.

FINDINGS

RT significantly delayed time to tumor quintupling compared to no RT (p < 0·0001) [two-way ANOVA], but no difference in tumor growth was seen between mice receiving isotype or 1E10Fc treatment regardless of concurrent RT. Lower microvessel density was observed in the 1E10Fc + RT group. Fewer mice treated with 1E10Fc had micrometastases, but this difference was not statistically significant (p < 0·09).

INTERPRETATION

1E10Fc did not act as a radiosensitizer in this primary STS model.

FUNDING

This study was funded by a research agreement from Eli Lilly and Company.

β-Arrestin Based Receptor Signaling Paradigms: Potential Therapeutic Targets for Complex Age-Related Disorders

G protein coupled receptors (GPCRs) were first characterized as signal transducers that elicit downstream effects through modulation of guanine (G) nucleotide-binding proteins. The pharmacotherapeutic exploitation of this signaling paradigm has created a drug-based field covering nearly 50% of the current pharmacopeia. Since the groundbreaking discoveries of the late 1990s to the present day, it is now clear however that GPCRs can also generate productive signaling cascades through the modulation of β-arrestin functionality. β-Arrestins were first thought to only regulate receptor desensitization and internalization - exemplified by the action of visual arrestin with respect to rhodopsin desensitization. Nearly 20 years ago, it was found that rather than controlling GPCR signal termination, productive β-arrestin dependent GPCR signaling paradigms were highly dependent on multi-protein complex formation and generated long-lasting cellular effects, in contrast to G protein signaling which is transient and functions through soluble second messenger systems. β-Arrestin signaling was then first shown to activate mitogen activated protein kinase signaling in a G protein-independent manner and eventually initiate protein transcription - thus controlling expression patterns of downstream proteins. While the possibility of developing β-arrestin biased or functionally selective ligands is now being investigated, no additional research has been performed on its possible contextual specificity in treating age-related disorders. The ability of β-arrestin-dependent signaling to control complex and multidimensional protein expression patterns makes this therapeutic strategy feasible, as treating complex age-related disorders will likely require therapeutics that can exert network-level efficacy profiles. It is our understanding that therapeutically targeting G protein-independent effectors such as β-arrestin will aid in the development of precision medicines with tailored efficacy profiles for disease/age-specific contextualities.

Systemic Anti-Cancer Therapy in Synovial Sarcoma: A Systematic Review

Synovial sarcoma (SS) is an aggressive malignancy which accounts for approximately 5–10% of all soft-tissue sarcomas. SS has pathologic and genomic characteristics that define it as a distinct subtype of soft tissue sarcoma (STS). STS subtypes continue to be recognized as distinct entities with specific characteristics, including differential chemo-sensitivity. The objective of this study was to conduct a descriptive review of current data on survival outcomes of systemic anti-cancer therapy specific to SS. A systematic literature review was conducted, using a custom search strategy to search EMBASE, Medline and CENTRAL for clinical trials and observational studies reporting overall survival (OS), progression-free survival (PFS) and/or response for cohorts of at least 50 SS patients. We identified 28 studies meeting these criteria, 25 of which were retrospective studies. Only three prospective studies were identified. Survival reports varied widely between studies based on the population, in particular on the disease stage, and reporting was heterogeneous in terms of the time points reported on. For patients with localized disease, reports of five-year PFS ranged from 26% to 80.7% and five-year OS from 40% to 90.7%, whereas five-year OS for patients with metastatic disease was very low at around 10%; and in one case, 0% was reported. Only four of the included publications reported outcomes by type of systemic anti-cancer therapy received. Our study draws attention to the fact that additional prospective studies to better define the most appropriate treatment for SS in all stages and lines of therapy are still needed.

Novel 2-phenyloxypyrimidine derivative induces apoptosis and autophagy via inhibiting PI3K pathway and activating MAPK/ERK signaling in hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is the second leading cause of cancer-related mortality globally. Because most patients are diagnosed at advanced stages of the disease, multi-targeted tyrosine kinase inhibitor sorafenib is the only available drug to show limited effectiveness. Novel and effective therapies are unmet medical need for advanced HCC patients. Given that the aberrant expression and activity of platelet-derived growth factor receptor α (PDGFRα) are closely associated with the pathogenesis of HCC, here we present the discovery and identification of a novel PDGFRα inhibitor, N-(3-((4-(benzofuran-2-yl)pyrimidin-2-yl)oxy)-4-methylphenyl)-4-((4-methylpiperazin-1-yl)methyl)benzamide (E5) after comparison of different derivatives. We found that E5 inhibited proliferation and induced apoptosis in HCC cells. Since the pan-caspase inhibitor Z-VAD-FMK partially rescued HCC cells from E5-reduced cell viability, autophagic cell death triggered by E5 was subsequently investigated. E5 could induce the conversion of LC3-I to LC3-II, increase the expression of Atg5 and restore the autophagy flux blocked by chloroquine. Meanwhile, E5 was able to downregulate the PDGFRα/PI3K/AKT/mTOR pathway and to activate MAPK/ERK signaling pathway. Taken together, in addition to the possibility of E5 as a valuable drug candidate, the present study further supports the notion that targeted inhibition of PDGFRα is a promising therapeutic strategy for HCC.

Kinases and Cancer

Protein kinases are a large family of enzymes catalyzing protein phosphorylation. The human genome contains 518 protein kinase genes, 478 of which belong to the classical protein kinase family and 40 are atypical protein kinases [...].

Developments in the management of advanced soft-tissue sarcoma - olaratumab in context

Lartruvo® (olaratumab) is a fully human immunoglobulin G subclass 1 (IgG1) monoclonal antibody that inhibits platelet-derived growth factor receptor alpha (PDGFRα). The antitumor activity of olaratumab has been tested in vitro and in vivo, and inhibition of tumor growth has been observed in cancer cell lines, including glioblastoma and leiomyosarcoma cells. It represents the first-in-class antibody to be approved by regulatory authorities for the treatment of advanced soft-tissue sarcomas (STSs) in combination with doxorubicin, based on the results of the Phase Ib/II trial by Tap et al. The median progression-free survival (PFS), which was the primary end point of the study, was improved for patients treated with olaratumab plus doxorubicin compared to those treated with doxorubicin monotherapy (6.6 vs 4.1 months, respectively; HR 0.672, 95% CI 0.442-1.021, p=0.0615). Moreover, final analysis of overall survival (OS) showed a median OS of 26.5 months with olaratumab plus doxorubicin vs 14.7 months with doxorubicin, with a gain of 11.8 months (HR 0.46, 95% CI 0.30-0.71, p=0.0003). In October 2016, olaratumab was admitted in the Accelerated Approval Program by the US Food and Drug Administration (FDA) for use in combination with doxorubicin for the treatment of adult patients with STSs. In November 2016, the European Medicines Agency (EMA) granted conditional approval for olaratumab in the same indication under its Accelerated Assessment Program. A double-blind, placebo-controlled, randomized Phase III study (ANNOUNCE trial, NCT02451943) is being performed in order to confirm the survival advantage of olaratumab and to provide definitive drug confirmation by regulators. The study is ongoing, but enrollment is closed. The purpose of this review was to evaluate the rationale of olaratumab in the treatment of advanced STSs and its emerging role in clinical practice.