Phase 1, first-in-human study of TYRP1-TCB (RO7293583), a novel TYRP1-targeting CD3 T-cell engager, in metastatic melanoma: active drug monitoring to assess the impact of immune response on drug exposure

Introduction

Although checkpoint inhibitors (CPIs) have improved outcomes for patients with metastatic melanoma, those progressing on CPIs have limited therapeutic options. To address this unmet need and overcome CPI resistance mechanisms, novel immunotherapies, such as T-cell engaging agents, are being developed. The use of these agents has sometimes been limited by the immune response mounted against them in the form of anti-drug antibodies (ADAs), which is challenging to predict preclinically and can lead to neutralization of the drug and loss of efficacy.

Methods

TYRP1-TCB (RO7293583; RG6232) is a T-cell engaging bispecific (TCB) antibody that targets tyrosinase-related protein 1 (TYRP1), which is expressed in many melanomas, thereby directing T cells to kill TYRP1-expressing tumor cells. Preclinical studies show TYRP1-TCB to have potent anti-tumor activity. This first-in-human (FIH) phase 1 dose-escalation study characterized the safety, tolerability, maximum tolerated dose/optimal biological dose, and pharmacokinetics (PK) of TYRP1-TCB in patients with metastatic melanoma (NCT04551352).

Results

Twenty participants with cutaneous, uveal, or mucosal TYRP1-positive melanoma received TYRP1-TCB in escalating doses (0.045 to 0.4 mg). All participants experienced ≥1 treatment-related adverse event (TRAE); two participants experienced grade 3 TRAEs. The most common toxicities were grade 1-2 cytokine release syndrome (CRS) and rash. Fractionated dosing mitigated CRS and was associated with lower levels of interleukin-6 and tumor necrosis factor-alpha. Measurement of active drug (dual TYPR1- and CD3-binding) PK rapidly identified loss of active drug exposure in all participants treated with 0.4 mg in a flat dosing schedule for ≥3 cycles. Loss of exposure was associated with development of ADAs towards both the TYRP1 and CD3 domains. A total drug PK assay, measuring free and ADA-bound forms, demonstrated that TYRP1-TCB-ADA immune complexes were present in participant samples, but showed no drug activity in vitro.

Discussion

This study provides important insights into how the use of active drug PK assays, coupled with mechanistic follow-up, can inform and enable ongoing benefit/risk assessment for individuals participating in FIH dose-escalation trials. Translational studies that lead to a better understanding of the underlying biology of cognate T- and B-cell interactions, ultimately resulting in ADA development to novel biotherapeutics, are needed.

Imaging for assessment of cancer treatment response to immune checkpoint inhibitors can be complementary in identifying hypophysitis

Introduction

Hypophysitis is reported in 8.5%-14% of patients receiving combination immune checkpoint inhibition (cICI) but can be a diagnostic challenge. This study aimed to assess the role of routine diagnostic imaging performed during therapeutic monitoring of combination anti-CTLA-4/anti-PD-1 treatment in the identification of hypophysitis and the relationship of imaging findings to clinical diagnostic criteria.

Methods

This retrospective cohort study identified patients treated with cICI between January 2016 and January 2019 at a quaternary melanoma service. Medical records were reviewed to identify patients with a documented diagnosis of hypophysitis based on clinical criteria. Available structural brain imaging with magnetic resonance imaging (MRI) or computed tomography (CT) of the brain and 2-deoxy-2-[18F]fluoro-D-glucose positron emission tomography with computed tomography (FDG-PET/CT) were assessed retrospectively. The main radiological outcome measures were a relative change in pituitary size or FDG uptake temporally attributed to cICI.

Results

There were 162 patients (median age 60 years, 30% female) included. A total of 100 and 134 had serial CT/MRI of the brain and FDG-PET/CT, respectively. There were 31 patients who had a documented diagnosis of hypophysitis and an additional 20 who had isolated pituitary imaging findings. The pituitary gland enlargement was mild, and the largest absolute gland size was 13 mm, with a relative increase of 7 mm from baseline. There were no cases of optic chiasm compression. Pituitary enlargement and increased FDG uptake were universally transient. High-dose glucocorticoid treatment for concurrent irAEs prevented assessment of the pituitary-adrenal axis in 90% of patients with isolated imaging findings.

Conclusion

Careful review of changes in pituitary characteristics on imaging performed for assessment of therapeutic response to iICI may lead to increased identification and more prompt management of cICI-induced hypophysitis.

BRCA1 and BRCA2 carriers with breast, ovarian and prostate cancer demonstrate a different pattern of metastatic disease compared with non-carriers: results from a rapid autopsy programme

AIM

To catalogue and compare the pattern of metastatic disease in germline BRCA1/2 pathogenic mutation carriers and non-carriers with breast, ovarian and prostate cancer from a rapid autopsy programme.

METHODS AND RESULTS

The number of metastases in the major body systems and the proportion of participants with metastases were documented in 50 participants (19 germline mutation carriers). Analysis was conducted on the participants' pattern of disease for the different cancers and mutation subgroups. The four commonly affected organ systems were the digestive (liver only) (82%), respiratory (76%), gastrointestinal (65%) and reticuloendothelial (42%). There were significant differences in the pattern of metastatic breast cancer in BRCA1/2 germline carriers compared with non-carriers. Breast cancer carriers had significantly fewer organ systems involved (median n = 3, range = 1-3) compared with non-carriers (median n = 9, range = 1-7) (P = 0.03). BRCA1/2 carriers with ovarian carcinomas had significantly more organ systems with metastatic carcinoma (median n = 10, range = 3-8) than non-carriers (median n = 5, range = 3-5) (P < 0.001). There were no significant differences in the number of involved systems in BRCA2 carriers compared with non-carriers with prostate cancer (P = 1.0). There was an absence of locoregional disease (6.5%) compared with distant disease (93.5%) among the three cancer subtypes (P < 0.001). The majority of metastatic deposits (97%) collected during the autopsy were identified by recent diagnostic imaging.

CONCLUSION

Even though a major limitation of this study is that our numbers are small, especially in the breast cancer carrier group, the metastatic patterns of breast and ovarian cancers may be impacted by BRCA1/2 carrier status, suggesting that tumours derived from patients with these mutations use different mechanisms of dissemination. The findings may focus clinical diagnostic imaging for monitoring metastases where whole-body imaging resources are scant.

Multiomic analysis of homologous recombination-deficient end-stage high-grade serous ovarian cancer

High-grade serous ovarian cancer (HGSC) is frequently characterized by homologous recombination (HR) DNA repair deficiency and, while most such tumors are sensitive to initial treatment, acquired resistance is common. We undertook a multiomics approach to interrogate molecular diversity in end-stage disease, using multiple autopsy samples collected from 15 women with HR-deficient HGSC. Patients had polyclonal disease, and several resistance mechanisms were identified within most patients, including reversion mutations and HR restoration by other means. We also observed frequent whole-genome duplication and global changes in immune composition with evidence of immune escape. This analysis highlights diverse evolutionary changes within HGSC that evade therapy and ultimately overwhelm individual patients.

The genomic and immune landscape of long-term survivors of high-grade serous ovarian cancer

Fewer than half of all patients with advanced-stage high-grade serous ovarian cancers (HGSCs) survive more than five years after diagnosis, but those who have an exceptionally long survival could provide insights into tumor biology and therapeutic approaches. We analyzed 60 patients with advanced-stage HGSC who survived more than 10 years after diagnosis using whole-genome sequencing, transcriptome and methylome profiling of their primary tumor samples, comparing this data to 66 short- or moderate-term survivors. Tumors of long-term survivors were more likely to have multiple alterations in genes associated with DNA repair and more frequent somatic variants resulting in an increased predicted neoantigen load. Patients clustered into survival groups based on genomic and immune cell signatures, including three subsets of patients with BRCA1 alterations with distinctly different outcomes. Specific combinations of germline and somatic gene alterations, tumor cell phenotypes and differential immune responses appear to contribute to long-term survival in HGSC.

The changing role for extended resections in an era of advanced radiotherapy techniques and novel therapies in gynaecological malignancy

Pelvic exenteration, first described in 1948 and subsequently refined, may be offered as a last hope of cure to patients with recurrent or locally advanced pelvic tumours, where radiotherapy is not an option. It is a complex, morbid, ultra-radical procedure involving en-bloc resection of the female reproductive organs, lower urinary tract, and a portion of the rectosigmoid. This article discusses the evolution of and current indications for pelvic exenteration in gynaecologic oncology as well as the reasons for its decline: primary and secondary prevention of cervical cancer (the recurrence of which is the most common indication for exenteration); improvements in treatment of cervical, endometrial, vaginal and vulvar cancer in the primary and recurrent setting; and the advent of novel therapies.

IGNITE: A phase II signal-seeking trial of adavosertib targeting recurrent high-grade, serous ovarian cancer with cyclin E1 overexpression with and without gene amplification

5515

Background: Cyclin E1 gene amplification and protein over-expression is a marker of platinum resistance in high grade serous ovarian, fallopian tube or primary peritoneal cancer (HGSC), and may predict response to WEE1 inhibition. Adavosertib, a WEE1 inhibitor, has demonstrated activity in unselected women with recurrent ovarian and serous endometrial cancer. We aimed to evaluate the efficacy of adavosertib in women with recurrent platinum resistant HGSC with cyclin E1 over-expression, with and without gene amplification. Methods: IGNITE is a multicentre, phase 2 trial with 2 cohorts of women with recurrent platinum resistant HGSC. Tumors were assessed for cyclin E1 protein expression by IHC and CCNE1 copy number by FISH. Patients were assigned to Cohort 1 if tumors were cyclin E1 over-expressed (H-score>50) and amplified (≥8 copies), and Cohort 2 if tumors were overexpressed and nonamplified. Patients with evaluable disease by RECIST v1.1 or GCIG CA-125 criteria were included. Adavosertib 300mg PO was given daily on days 1-5 and 8-12 of a 21-day cycle. The primary endpoint was investigator assessed clinical benefit (CB) defined as absence of progression for ≥ 18 weeks. Here we present the 18-week response data for the first 32 patients treated from Cohort 2, with a data cut-off of August 2021. Results: Between Jan-2020 and May-2021, 32 patients were accrued to Cohort 2. Median age was 62 years (range 42-77) and 84% had received ≥2 prior lines of chemotherapy. Median cyclin E1 IHC H-score was 120 and 28 patients (88%) had measurable disease by RECIST. Median number of cycles commenced was 8 (range 1-19). Overall response rate (ORR) was 53% and CB rate was 61% for all evaluable patients. Seventeen patients (53%) required a dose reduction, most commonly for neutropenia or fatigue. Seventeen patients experienced ≥Grade 3 treatment related adverse event, and 4 patients (15%) discontinued due to toxicity. Conclusions: The efficacy results in a biomarker-selected cohort of patients are promising with a higher response rate than reported in previous studies of adavosertib in unselected women with recurrent HGSC. Duration of response and progression free survival data will be presented as data matures. Clinical trial information: ACTRN12619001185156P. [Table: see text]

NeoTrio: Randomized trial of neoadjuvant (NAT) pembrolizumab (Pembro) alone, in sequence (SEQ) with, or concurrent (CON) with dabrafenib plus trametinib (D+T) in resectable BRAF-mutant stage III melanoma to determine optimal combination of therapy

9503

Background: Combination anti-PD(L)1 and BRAF/MEK-targeted therapy (TT) improves PFS in stage IV melanoma vs TT. In stage IV melanoma recent data suggest immunotherapy 1st until progression, rather than BRAF-TT, improves OS, and induction TT upfront adds little benefit. NeoTrio explored the optimal combination of BRAF-TT and anti-PD1 using the NAT platform in pts with stage III melanoma (NCT02858921). Methods: 60 pts with resectable, RECIST measurable stage III (no in-transit) BRAFV600-mutant melanoma were randomized 1:1:1 to 3 arms of 6 wks of NAT followed by complete lymph node dissection (CLND): A) Pembro ALONE (200mg Q3W x 2); B) SEQ - D+T (150mg bd + 2mg od) for 1 wk followed by pembro (200mg x 2); C) CON – D+T+pembro (doses as SEQ). Pts had 46 wks pembro post-CLND. Primary endpoint was the pathological response rate (pRR) and pathological complete response (pCR) at wk 6. Secondary endpoints; RECIST RR at wk 6, event-free survival (EFS), RFS, OS, adverse events (AE) and translational endpoints. Results: At data cutoff 2 Jan 2022, 20 pts per arm had similar baseline characteristics; overall 42% female, med age 53 yrs, 82% BRAF V600E, 62% clinical N1b. Med f/u was 20 months (95% CI 17-31). The pCR rate and pRR were highest in CON arm, and similar in ALONE and SEQ arms (Table). Events (progression before surgery, recurrence after surgery or death) were highest in ALONE arm at this 1st analysis (Table). Assessment of the durability of path response subtypes in each arm is ongoing. Most common Rx related AE were fatigue (65%, 70%, 70%, ALONE, SEQ and CON respectively), pyrexia (0%, 25%, 85%) and rash (50%, 35%, 35%). Gd 3/4 AE occurred in 30%, 25% and 55%, respectively; pyrexia and hepatitis were common in CON during NAT. Rx interruptions during NAT occurred in 0, 3 and 19 pts, respectively; 1, 0 and 8 pts permanently discontinued. Post NAT surgical operability was the same or improved in 81%. Longitudinal analysis of melanoma tissue, microenvironment and microbiome is ongoing. Conclusions: CON D+T+pembro achieved the highest pRR, pCR rate, but with greater toxicity. Recurrences were seen in those with pCR/near pCR in BRAF-TT containing arms, but not in pembro ALONE, in keeping with previous data of NAT with checkpoint inhibitors vs BRAF-TT. Short course of D+T prior to PD1 did not improve path response, despite previous translational data showing increased tumour infiltrating T-cells early-during treatment with D+T. Follow up is ongoing. Clinical trial information: NCT02858921. [Table: see text]

Tissue-resident memory T cells from a metastatic vaginal melanoma patient are tumor-responsive T cells and increase after anti-PD-1 treatment

Background

Vaginal melanoma (VM) is a rare cancer and has a poor response to immune checkpoint blockade (ICB). CD8⁺Tissue Resident Memory (TRM) T cells proliferate in response to ICB and correlate with longer survival in metastatic cutaneous melanoma. However, their capacity to respond to VM and their neoantigens is not known.

Methods

Using longitudinal samples, we explored the evolution of VM mutations by whole-exome sequencing and RNAseq, we also defined the immune context using multiplex immunohistochemistry and nanostring pan cancer immune profile. Then using fresh single cell suspensions of the metastatic samples, we explored VM T cells via mass cytometry and single cell RNAseq and T cell receptor sequencing (TCRseq). Finally, we investigated TRM, pre-TRM and exhausted T cell function against melanoma neo-antigens and melanoma differentiation antigens in vitro.

Results

Primary VM was non-inflamed and devoid of CD8⁺ TRM cells. In contrast, both metastases showed proliferating CD8⁺ TRM were clustered at the tumor margin, with increased numbers in the second ICB-refractory metastasis. The first metastasis showed dense infiltration of CD8⁺ T cells, the second showed immune exclusion with loss of melanoma cell Major histocompatibility complex (MHC)-I expression associated with downregulation of antigen presentation pathway gene expression. CD8⁺ TRM from both metastases responded to autologous melanoma cells more robustly than all other CD8⁺ T cell subsets. In addition, CD8⁺ TRM shared TCR clones across metastases, suggesting a response to common antigens, which was supported by recognition of the same neoantigen by expanded tumor infiltrating lymphocytes.

Conclusions

In this study, we identified TRM clusters in VM metastases from a patient, but not primary disease. We showed TRM location at the tumor margin, and their superior functional response to autologous tumor cells, predicted neoantigens and melanoma differentiation antigens. These CD8⁺ TRM exhibited the highest tumor-responsive potential and shared their TCR with tumor-infiltrating effector memory T cells. This suggests VM metastases from this patient retain strong antitumor T cell functional responses; however, this response is suppressed in vivo. The loss of VG MHC-I expression is a common immune escape mechanism which was not addressed by anti-PD-1 monotherapy; rather an additional targeted approach to upregulate MHC-I expression is required.

Characterization of the treatment-naive immune microenvironment in melanoma with BRAF mutation

Background

Patients with BRAF-mutant and wild-type melanoma have different response rates to immune checkpoint blockade therapy. However, the reasons for this remain unknown. To address this issue, we investigated the precise immune composition resulting from BRAF mutation in treatment-naive melanoma to determine whether this may be a driver for different response to immunotherapy.

Methods

In this study, we characterized the treatment-naive immune context in patients with BRAF-mutant and BRAF wild-type (BRAF-wt) melanoma using data from single-cell RNA sequencing, bulk RNA sequencing, flow cytometry and immunohistochemistry (IHC).

Results

In single-cell data, BRAF-mutant melanoma displayed a significantly reduced infiltration of CD8⁺ T cells and macrophages but also increased B cells, natural killer (NK) cells and NKT cells. We then validated this finding using bulk RNA-seq data from the skin cutaneous melanoma cohort in The Cancer Genome Atlas and deconvoluted the data using seven different algorithms. Interestingly, BRAF-mutant tumors had more CD4⁺ T cells than BRAF-wt samples in both primary and metastatic cohorts. In the metastatic cohort, BRAF-mutant melanoma demonstrated more B cells but less CD8⁺ T cell infiltration when compared with BRAF-wt samples. In addition, we further investigated the immune cell infiltrate using flow cytometry and multiplex IHC techniques. We confirmed that BRAF-mutant melanoma metastases were enriched for CD4⁺ T cells and B cells and had a co-existing decrease in CD8⁺ T cells. Furthermore, we then identified B cells were associated with a trend for improved survival (p=0.078) in the BRAF-mutant samples and Th2 cells were associated with prolonged survival in the BRAF-wt samples.

Conclusions

In conclusion, treatment-naive BRAF-mutant melanoma has a distinct immune context compared with BRAF-wt melanoma, with significantly decreased CD8⁺ T cells and increased B cells and CD4⁺ T cells in the tumor microenvironment. These findings indicate that further mechanistic studies are warranted to reveal how this difference in immune context leads to improved outcome to combination immune checkpoint blockade in BRAF-mutant melanoma.

Treatment patterns after poly-ADP ribose polymerase (PARP) inhibitors in epithelial ovarian cancer patients

OBJECTIVES

The primary objective of this study was to describe treatment patterns after poly-ADP ribose polymerase (PARP) inhibitor in patients with epithelial ovarian cancer. Secondary objectives were to evaluate duration of response, time to first subsequent therapy, progression-free survival and overall survival.

METHODS

This was a retrospective analysis of patients with epithelial ovarian cancer treated with PARP inhibitor therapy at six Australian gynecological oncology centers. Eligible patients were identified via clinics, trial databases and pharmacy dispensing logs between January 2005 and September 2019. Information regarding clinico-pathological characteristics and treatment outcomes were collated from medical records.

RESULTS

A total of 85 patients with epithelial ovarian cancer were identified. Of these, 61% had germline BRCA1/2 mutations, 9% had somatic BRCA1/2 mutations, 5% had confirmed homologous recombination deficiency and 25% were BRCA1/2 wildtype mutations. A total of seventy-seven (91%) patients received chemotherapy after PARP inhibitor, with fifty-six (72.7%) of these patients receiving platinum-based chemotherapy. Four patients (5%) had a complete response, 15 (20%) a partial response, 15 (20%) stable disease and 41 (55%) progressive disease. Median duration of response to chemotherapy was 7.0 months (range 0.2-20.4). Median time to first subsequent therapy was 17.6 and 15.1 months in patients who received a PARP inhibitor as maintenance therapy and treatment, respectively. Median progression-free survival of first line treatment after PARP inhibitor was 9.6, 3.5 and 4.6 months for platinum doublet, single agent platinum and non-platinum chemotherapy, respectively. Adjusting for age and FIGO (Federation of Gynecological Oncologists classification) stage progression-free survival did not differ between treatment groups (p=0.14). Median overall survival for the cohort was 69 months, and patients with platinum sensitive ovarian cancer had improved survival compared with those with platinum refractory or resistant disease.

CONCLUSION

Platinum doublet chemotherapy resulted in non-significant improved progression-free survival compared with other regimens, suggesting potential independent mechanisms of resistance between PARP inhibitor and platinum compounds.

Efficacy of immune checkpoint inhibitors for in-transit melanoma

BACKGROUND

The efficacy of immune checkpoint inhibitors (ICI) in metastatic melanoma is well established. However, there are limited data regarding their efficacy in in-transit melanoma (ITM). This study assessed the efficacy of ICI in patients with ITM.

METHODS

A retrospective review of patients with ITM commenced on an ICI between March 2013 and February 2018 at three tertiary centers in Australia. Patients were excluded if they had previous or synchronous distant metastases. Overall response rate (ORR), progression-free survival (PFS) and overall survival (OS) were based on a composite of radiological and clinical assessments.

RESULTS

Fifty-four patients were included: 27 (50%) female; median age 75 (range 26-94); 12 (22%) stage IIIB, 40 (74%) stage IIIC and 2 (4%) stage IIID; 10 (19%) BRAF mutant. Forty (74%) received single-agent anti-PD-1 (pembrolizumab or nivolumab), 8 (15%) single agent anti-CTLA-4 (ipilimumab), 5 (9%) combination anti-PD-1/anti-CTLA-4 (ipilimumab and nivolumab or pembrolizumab) and 1 (2%) combination anti-PD-L1 (atezolizumab) and MEK inhibitor (cobimetinib). The median follow-up was 15 months (2-46).ORR to ICI was 54%: 14 (26%) complete responses; 15 (28%) partial responses; 9 (17%) stable disease; 16 (30%) progressive disease. Thirteen (46%) responders had only one ITM lesion. ORR was 58% for single-agent anti-PD-1, 38% for single-agent anti-CTLA4 and 40% for anti-PD-1/anti-CTLA-4. The median PFS was 11.7 months (6.6-not reached). 1-year and 2-year PFS were 48% and 39%, respectively,. Fourteen progressed locoregionally and 11 progressed distantly. The median OS was not reached. 1-year and 2-year OS were 85% and 63%, respectively. No clinicopathological features were associated with ORR.

CONCLUSIONS AND RELEVANCE

ICI produce objective responses in ITM and should be considered in patients with unresectable ITM or disease recurrence.

Abstract LB104: Dose-Finding/Expansion Phase Ib Study to Evaluate the Safety and Activity of BET Inhibitor RO6870810 (RO) and Atezolizumab (A) in Patients (pts) with Advanced Ovarian Cancer (OC) or Triple Negative Breast Cancer (TNBC)

Background: Transcriptional activation of c-MYC through bromodomain and extra-terminal (BET) proteins contributes to the malignant phenotype of OC and TNBC. RO is a novel thienodiazepine, small molecule, non-covalent inhibitor of the BET family of bromodomains. BET inhibition may also play a role in immune modulation via downregulation of CD47 and PD-L1. We hypothesized that RO may enhance the clinical potential of A. We report results of a phase 1b study of RO in combination with A in advanced OC and TNBC (NCT03292172). Methods: Patients with advanced OC or TNBC were eligible. In the dose escalation part, pts received subcutaneous escalating doses of RO (0.30, 0.45, 0.65 mg/kg) on days 1 - 14 of 21-day cycles in combination with A at 1200 mg IV on Day 1 of each cycle. In the expansion part, pts received RO at 0.45 mg/kg. Primary objectives were safety, tolerability and preliminary clinical activity of the combination. Results: Between Nov 2017 and Dec 2018, a total of 36 pts were enrolled, 27 pts in the dose escalation and 9 pts in the expansion part at 6 sites in the US, Canada, Denmark and Australia. The median age was 53 (34 - 72) years. 99 total cycles were completed, with a median of 2 (1-14) cycles per pt. During dose escalation, one pt at 0.65 mg/kg + A experienced a DLT of Grade 3 febrile neutropenia. Grade ≥ 3 treatment emergent AEs in ≥ 5% of all pts were immune-related AEs (irAEs) associated with laboratory findings suggestive of secondary hemophagocytic lymphohistiocytosis (HLH), anemia and hyponatremia (11.1% each), abdominal pain, fatigue and small intestinal obstruction (8.3% each), thrombocytopenia, ALT increased and hyperglycemia (5.6% each). Organ toxicities associated with the 4 cases of suspected HLH included fever and febrile neutropenia, myocarditis, encephalitis and pneumonitis; there was no clear correlation between RO exposure and these events. irAEs were observed in an additional 4 pts. AEs leading to treatment discontinuation were reported in 22.2% of pts, with suspected HLH being the most common AE (11.1%). A total of 15 deaths were reported in the study: 9 deaths due to progressive disease, and 6 deaths reported during long-term follow-up where the cause of death was reported as unknown. Two PRs were noted; one each at 0.30 mg/kg + A and at 0.45 mg/kg + A. 15 pts had SD and 14 pts had PD as best response. Median duration of disease control was 93 (95% CI 51-178) days. Response assessment of 5 pts was missing. Conclusions: While suspected HLH/HLH is rare for RO or A given as monotherapy, the safety profile of the combination was considered unacceptable as noted by the high frequency and severity of irAEs including suspected HLH. A limited anti-tumor activity was observed with PR as best overall response in 2 pts. The trial was terminated early due to the unfavorable risk-benefit profile.

Citation Format: Stephanie Lheureux, Iben Spangaard, Erika Hamilton, George Au-Yeung, Debra Richardson, Mark DeMario, Emily Labriola-Tompkins, Barbara Brennan, Eveline Nueesch, Evelyne Chesne, Izolda Franjkovic, Katharina Lechner, Martin Kornacker, Geoffrey I. Shapiro. Dose-Finding/Expansion Phase Ib Study to Evaluate the Safety and Activity of BET Inhibitor RO6870810 (RO) and Atezolizumab (A) in Patients (pts) with Advanced Ovarian Cancer (OC) or Triple Negative Breast Cancer (TNBC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB104.

Clinical, FDG-PET and molecular markers of immune checkpoint inhibitor response in patients with metastatic Merkel cell carcinoma

BACKGROUND

Metastatic Merkel cell carcinoma (mMCC) is an aggressive neuroendocrine malignancy of the skin with a poor prognosis. Immune checkpoint inhibitors (ICIs) have shown substantial efficacy and favorable safety in clinical trials.

METHODS

Medical records of patients (pts) with mMCC treated with ICIs from August 2015 to December 2018 at Peter MacCallum Cancer Centre in Australia were analyzed. Response was assessed with serial imaging, the majority with FDG-PET/CT scans. RNA sequencing and immunohistochemistry for PD-L1, CD3 and Merkel cell polyomavirus (MCPyV) on tumor samples was performed.

RESULTS

23 pts with mMCC were treated with ICIs. A median of 8 cycles (range 1 to 47) were administered, with treatment ongoing in 6 pts. Objective responses (OR) were observed in 14 pts (61%): 10 (44%) complete responses (CR) and 4 (17%) partial responses (PR). Median time to response was 8 weeks (range 6 to 12) and 12-month progression-free survival rate was 39%. Increased OR were seen in pts aged less than 75 (OR 80% vs 46%), no prior history of chemotherapy (OR 64% vs 50%), patients with an immune-related adverse event (OR 100% vs 43%) and in MCPyV-negative tumors (OR 69% vs 43%). Pts with a CR had lower mean metabolic tumor volume on baseline FDG-PET/CT scan (CR: 35.7 mL, no CR: 187.8 mL, p=0.05). There was no correlation between PD-L1 positivity and MCPyV status (p=0.764) or OR (p=0.245). 10 pts received radiation therapy (RT) during ICI: 4 pts started RT concurrently (OR 75%, CR 50%), 3 pts had isolated ICI-resistant lesions successfully treated with RT and 3 pts with multisite progression continued to progress despite RT. Overall, 6 pts (26%) had grade 1-2 immune-related adverse events.

CONCLUSION

ICIs showed efficacy and safety in mMCC consistent with trial data. Clinical and imaging predictors of response were identified.

Noncanonical IL6 Signaling-Mediated Activation of YAP Regulates Cell Migration and Invasion in Ovarian Clear Cell Cancer

Ovarian clear cell adenocarcinoma (OCCA) is characterized by a particularly poor response to conventional chemotherapy and a short overall survival time in women with established disease. The development of targeted treatments for OCCA relies on a better understanding of its molecular characteristics. IL6 is strongly expressed in OCCA and may therefore provide a novel therapeutic target. Here we use CRISPR/Cas9 and conditional short hairpin interfering RNA to perform loss-of-function studies in human OCCA cell lines to explore the requirement for IL6 in vitro and in vivo. While reduction of IL6 expression exerted limited effects in vitro, its attenuation significantly impaired tumor growth and neovascularization in vivo. In contrast to typical signaling via STAT3, IL6 in OCCA signaled via a noncanonical pathway involving gp130, Src, and the Hippo pathway protein YAP. A high-throughput combination drug screen identified agents that enhanced cell killing following reduction of IL6 signaling. Intersection of screen hits obtained from two cell lines and orthogonal approaches to attenuation of IL6 yielded AKT and EGFR inhibitors as enhancers of the inhibitory monoclonal IL6 receptor antibody tocilizumab. This study defines for the first time the requirements for, and mechanisms of, signaling by IL6 in human OCCA cell lines and identifies potential combinatory therapeutic approaches. Given the molecular diversity of OCCA, further in vitro and in vivo studies are warranted to determine whether such approaches will overcome the limited efficacy of tocilizumab observed in ovarian cancer to date. SIGNIFICANCE: This study defines the requirements for and mechanisms of noncanonical signaling by IL6 in human ovarian clear cell adenocarcinoma cell lines and identifies combinatory therapeutic approaches to be explored clinically.

Abstract IA04: Drug resistance in end-stage high-grade serous ovarian cancer

Background: Acquired drug resistance is the major obstacle in controlling high-grade serous ovarian cancer (HGSC) and leads to poor overall survival. Comparatively little massively parallel sequencing data exist from HGSC patients with recurrent or end-stage disease who have been extensively treated with chemotherapy or newer targeted agents, such as antiangiogenics or PARP inhibitors (PARPi). We previously identified four mechanisms of acquired resistance from whole-genome sequencing (WGS) of 23 HGSC patients with recurrent disease; a resistance mechanism of any kind was only identified in half of the patients.

Aim: To characterize genomic features and identify mechanisms of acquired drug resistance in end-stage HGSC patients.

Methods: Since 2012, we have collected tumor samples from 19 HGSC patients through our rapid-autopsy program. On average, we collect 17 tumor sites per patient during the autopsy, which is performed a median 6 hours after death. SNP array, WGS, and RNA sequencing were performed to detect germline and somatic mutations, copy number alterations and gene expression patterns.

Results: A total of 89 end-stage tumor samples from 15 patients with germline or somatic mutations in components of the homologous recombination (HR) DNA repair pathway have been analyzed by SNP array, and a subset of those have undergone WGS (n=44) and RNAseq (n=47). As expected, all samples had a somatic pathogenic TP53 mutation and have highly aberrant somatic copy number profiles. Prominent mutational signatures (single- and double-base substitutions) are associated with defective HR and prior treatment with platinum drugs. The total single-base substitution mutation burden is similar across tumor samples within patients; however, many mutations are unique to individual tumor samples. Currently, reversion mutations, which are secondary mutations in HR genes, are the most common resistance mechanism identified in our cohort of end-stage patients.

Conclusion: Our data are allowing us to understand HGSC at end stage, by examining the catalogue of resistance mechanisms within an individual patient and reconstructing the natural history of HGSC.

Citation Format: Elizabeth L. Christie, Kathryn Alsop, George Au-Yeung, Ahwan Pandey, Australian Ovarian Cancer Study, David D.L. Bowtell. Drug resistance in end-stage high-grade serous ovarian cancer [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research; 2019 Sep 13-16, 2019; Atlanta, GA. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(13_Suppl):Abstract nr IA04.

Abstract A48: Antiapoptotic gene expression and sensitivity to BH3-mimetics in chemoresistant, high-grade serous ovarian cancer cell lines

Introduction: The development of chemotherapy resistance is common in relapsed high-grade serous ovarian cancer (HGSOC). An understanding of mechanisms that are associated with the development of chemotherapy resistance in the clinical setting is needed to improve treatment outcomes. In this study, cell lines newly derived from patients with relapsed HGSOC were characterized at a molecular level to determine associations with response to commonly used chemotherapy drugs. RNA sequencing combined with high-throughput drug library screening was used to determine potential resistance mechanisms and identify drugs and combinations that may be effective in chemoresistant HGSOC.

Methods: Six ovarian cancer cell lines derived from ascites of relapsed HGSOC patients who had developed chemoresistant disease were characterized using multigene panel mutation testing, whole-genome DNA copy number analysis, and RNA sequencing. Drug responses to carboplatin and paclitaxel were determined using the CellTitre 96® AQueous One Solution Cell Proliferation Assay (Promega). For two of the resistant cell lines, high-throughput drug screens using three drug libraries—NCI-Approved Oncology Drug set (101 compounds), Kinase Inhibitor Library (210 compounds), and Targeted Agent Library (73 compounds)—were carried out to identify agents with activity in these resistant models. Apoptosis activation was measured using CellPlayer Caspase 3/7 assay (Essen Bioscience). Sensitivity to BH3-mimetics, ABT-737 and navitoclax (ABT-263), was tested in three of the cell lines and in one line, the effects of combining these agents with paclitaxel were assessed using CompuSyn.

Results: TP53 mutations were identified in all cell lines, consistent with high-grade serous histology, and all lines were relatively resistant to carboplatin. AOCS5 and AOCS15 were the most resistant to carboplatin and AOCS5 was also highly resistant to paclitaxel. Drug library screens carried out on both AOCS5 and AOCS15 showed differential sensitivity to a number of drug classes. While AOCS5 was found to be generally resistant to most drugs, it was sensitive to ABT-737. RNA-seq identified relative overexpression of antiapoptotic genes in AOCS5, in particular BCL2L1, BCL2, and BCL2L2, in comparison to the other five cell lines. AOCS5 was more sensitive to navitoclax and ABT-737 compared with cell lines that did not overexpress antiapoptotic genes. Combining BH3-mimetics and paclitaxel showed synergism in the highly paclitaxel-resistant cell line AOCS5.

Conclusion: Inhibition of apoptosis was identified as a potential mechanism of paclitaxel resistance, and overexpression of antiapoptotic genes may constitute a biomarker profile to predict sensitivity to BH3-mimetics in relapsed HGSOC.

Citation Format: Cristina Mapagu, Sivatharsny Srirangan, George Au-Yeung, Australian Ovarian Cancer Study, Paul R. Harnett, David D. Bowtell, Anna deFazio. Antiapoptotic gene expression and sensitivity to BH3-mimetics in chemoresistant, high-grade serous ovarian cancer cell lines [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research; 2019 Sep 13-16, 2019; Atlanta, GA. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(13_Suppl):Abstract nr A48.

A closer look at immune-mediated myocarditis in the era of combined checkpoint blockade and targeted therapies

Immune checkpoint inhibitors (ICI) and tyrosine kinase inhibitors (TKI) have transformed the management of many malignancies. Although rare, immune-mediated myocarditis presents unique clinical challenges due to heterogenous presentation, potential life-threatening consequences, and the time-critical need to differentiate it from other causes of cardiac dysfunction. Increasingly, TKI are being combined with ICI to promote immune modulation and improve efficacy. However, these combinations are associated with more toxicities. This series describes six patients with advanced melanoma who developed immune-mediated myocarditis while receiving an anti-PD-1 antibody or an anti-PD-L1 antibody plus a mitogen-activated protein kinase inhibitor. It provides a review of their heterogenous clinical presentations, investigational findings and treatment outcomes. Presentations ranged from asymptomatic cardiac enzyme elevation to death due to heart failure. We highlight the role of cardiac MRI (CMRI), a sensitive and non-invasive tool for the early detection and subsequent monitoring of myocardial inflammation. Five of the six patients exhibited CMRI changes characteristic of myocarditis, including mid-wall myocardial oedema and late gadolinium enhancement in a non-coronary distribution. Critically, two of these patients had normal findings on echocardiogram. Of the five patients who received immunosuppression, four recovered from myocarditis and one died of cardiac failure. The sixth patient improved with cardiac failure management alone. Three of the four patients responding to ICI derived long-term benefit. Clinical vigilance, prompt multimodal diagnosis and multidisciplinary management are paramount for the treatment of immune-mediated myocarditis.

FDG-PET metabolic tumor volume in advanced melanoma treated with ipilimumab and nivolumab (ipi/nivo)

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Background: Predictors of outcomes of immune checkpoint inhibitors (ICI) are desirable. We aim to investigate the prognostic value of 18F-fluorodeoxyglucose-PET/CT (FDG-PET) parameters at baseline and response monitoring of patients (pts) with advanced melanoma receiving ipi/nivo. Methods: From 2016-2019, melanoma pts who received ipi/nivo and had PET Response Criteria In Solid Tumors (PERCIST) measurable lesions on baseline FDG-PET were included. Baseline whole-body metabolic tumor volume (wbMTV), tumor stage, mutational status, ECOG performance score, lactate dehydrogenase (LDH) and treatment-line were correlated with overall survival (OS) in univariate and multivariate Cox-regression analysis. Response were assessed for a subset of pts with post-treatment FDG-PET based on PERCIST. Results: Of 162 pts receiving ipi/nivo, 122 pts (median age: 61; male: 73%; ECOG 0: 78%; raised LDH: 52%; M1c: 39%, M1d: 45% and BRAFV600E/Kmutation: 45%) met eligibility criteria. Forty percent received ipi/nivo as first-line treatment, 48% as second-line (25% post BRAF inhibitor(i)/MEKi and 23% post single-agent ICI) and 12% as third-line. At median follow-up of 21 months (mths), median OS was 20 mths (95% CI 11-not reached[NR]). Pts with above the median wbMTV had shorter OS than those with below the median wbMTV (NR vs 10 mths, 95% CI 8-NR; HR 2.0, 95% CI 1.2-3.4, p = 0.009). In multivariate analysis, wbMTV, ECOG and treatment-line were independently associated with OS. In 106 pts with post-treatment FDG-PET, 24 mths OS rate was higher for those with objective response (OR): 91% (95% CI 82-100%) vs stable disease:55% (27-100%) vs progressive disease:17% (8-35%) as best response, p < 0.001. OR was higher in first-line compared to second or third-line treatment, 75% vs 29-33% vs 23%, respectively, p = 0.0012. Conclusions: Increased baseline FDG-PET wbMTV is an independent prognostic biomarker in pts with advanced melanoma receiving ipi/nivo. FDG-PET response accurately predicts outcome. [Table: see text]

Do assumptions in health economic evaluations hamper drug uptake?

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Background: Health economic studies of anti-cancer systemic treatments typically make strong assumptions regarding the number of drug lines received after initial therapy. This may have a substantial effect on health economic outcomes and impact drug reimbursement and uptake in practice. This study aims to quantify the real-world systemic treatment patterns in 4 metastatic cancers using clinical registries to explore whether health economic assumptions are justifiable. Methods: Data from 4,431 metastatic cancer patients were extracted from Australian clinical registries: colorectal (COL, n = 3087), non-small cell lung (LUN, n = 705), pancreatic (PAN, n = 459), and melanoma (MEL, n = 180). A set of criteria was defined to consistently identify drug lines across the cancer-specific registries. These criteria were based on the type of drug (biological agent or chemotherapy), switches in chemotherapy regimen (whether a chemotherapy agent was added or removed) and the timing of such changes. Consequently, the identified drug lines provide a more detailed view on treatment patterns compared to clinical treatment lines (defined by disease progression), the latter typically including multiple drug lines. Censoring in the number of drug lines received due to ongoing treatment was accounted for in all analyses. Results: Most patients started treatment after diagnosis: 77% (COL), 89% (LUN), 56% (PAN) and 79% (MEL). For COL, LUN, PAN and MEL respectively, the proportion of patients starting a 2nd drug line was 51%, 60%, 19% and 24%, whereas 28%, 35%, 6% and 8% of patients started a 3rd drug line. In all cancers, patients were most likely to receive only a single drug line, i.e. the mode number of drug lines was 1. For all patients, the median number of drug lines were COL: 2, LUN: 2, PAN: 1, MEL: 1. For treated patients only, the median (range) number of drug lines received was COL: 2 (1-9), LUN: 2 (1-8), PAN: 1 (1-5), MEL: 1 (1-5). Conclusions: We show that patients are most likely to receive a single drug line. Considering our findings, most health economic analyses likely overestimate the intensity of drug treatment in metastatic disease, thereby underestimating the impact of initial treatment relative to downstream treatments. This is likely to bias estimates of total treatment cost, cost-effectiveness and budget impact, which will hamper the uptake of novel anti-cancer agents and may lead to suboptimal decisions regarding treatment strategies.

Evaluating the impact of dose reductions and delays on progression-free survival in women with ovarian cancer treated with either three-weekly or dose-dense carboplatin and paclitaxel regimens in the national prospective OPAL cohort study

OBJECTIVES

To determine the impact of chemotherapy dose reductions and dose delays on progression-free survival (PFS) in women with ovarian cancer receiving first line chemotherapy in a real world prospective cohort study.

METHODS

Patients with newly diagnosed epithelial ovarian (or peritoneal, fallopian tube) cancer enrolled in a national Australian prospective study, OPAL, who commenced three-weekly carboplatin (AUC 5 or 6) and paclitaxel 175 mg/m² (CP) or carboplatin (AUC 5 or 6) and dose-dense weekly paclitaxel 80 mg/m² (DD-CP) were eligible. Primary endpoint was PFS.

RESULTS

634 evaluable patients, 309 commenced CP and 325 DD-CP. Patient's age was similar in the two groups (median 62 years, range 21-79). All planned chemotherapy doses were completed by 66% vs 40% (p < 0.001) in the CP and DD-CP groups respectively. There was at least one treatment delay in 28% vs 58% (p < 0.001) in the CP and DD-CP groups, respectively, and 29% vs 49% (p < 0.001), respectively, required at least a 15% dose reduction for either carboplatin or paclitaxel. Median PFS was 29.2 [22.9, 43.8] and 21.5 [19.4, 23.1] months in the CP and DD-CP groups respectively. Adjusting for age, histology and FIGO stage PFS did not differ between treatment groups. Median PFS was similar in patients irrespective of dose reduction or dose delay.

CONCLUSION

Patients receiving DD-CP required more dose reductions and delays due to haematological toxicities and lower completion rates than CP without significant difference in median PFS between CP and DD-CP. Median PFS was similar in patients irrespective of dose reduction or dose delay.

OR32-06 Opportunistic Assessment of Pituitary Gland with Routine MRI and PET/CT Can Guide in Earlier and Increased Identification of Hypophysitis in Patients Treated with Combination Checkpoint Inhibitors

Background: Hypophysitis is one of the commonly reported adverse events related to immune checkpoint inhibitors (ICI), and the incidence is expected to rise with increased use of combined programmed cell death protein 1 (PD1) and cytotoxic T lymphocyte associated protein 4 (CTLA4) blockade. The clinical diagnosis can be delayed due to non-specific symptoms. At our centre, subjects undergo periodic imaging to assess tumour response to ICI. We reviewed whether neuroimaging studies can guide us in the diagnosis of hypophysitis and whether early changes can be detected before the onset of the clinical syndrome. Methods: We retrospectively reviewed the medical charts, biochemistry, structural brain imaging and whole-body positron emission tomography (PET) with specific reference to hypophysitis in 162 patients treated with combination ICI at a tertiary melanoma referral centre. Suspected cases were identified based on meeting one or more of the following criteria: 1) A documented diagnosis of hypophysitis or pituitary dysfunction found on chart review, 2) A relative change in pituitary size or appearance from baseline on neuroimaging studies, or 3) An increase in pituitary maximum standardized uptake value (SUVmax) greater than 25% from baseline on ¹⁸F-FDG PET. Results: 58/162 patients (36%) met criteria for suspected hypophysitis. Only 4 patients were identified on routine screening of early morning cortisol. 14 patients presented with symptoms leading to biochemical work up. A further 40 patients were found to have suspicious imaging changes, 13 of which went on to receive a formal diagnosis of hypophysitis. Of the remaining 27 patients, 23 were receiving high dose glucocorticoids for concomitant immune related adverse events at the time of the abnormal imaging study.Conclusion: We report the highest incidence to date of suspected hypophysitis in cohort of patients treated with combination ICI. This study highlights the important role of structural and functional neuroimaging in the early recognition of hypophysitis. Imaging may also play a role when the clinical syndrome is masked by concurrent glucocorticoid use.

SUN-127 Diagnostic Challenges Associated with the Rising Incidence of Endocrine Toxicity in the Era of Combination Immunotherapy

Background: Immune checkpoint blockade is now established as standard of care in several malignancies. Trials involving combined cytotoxic T lymphocyte associated protein 4 (CTLA4) and programmed cell death protein 1 (PD1) blockade demonstrate improved tumour responses in melanoma but at the cost of severe grade 3-4 immune related adverse events (irAEs) in 55%, and endocrine irAEs in up to 10% [1]. Immune-mediated damage to endocrine glands can be a diagnostic and management challenge. We aimed to review the incidence, biochemical evolution and imaging findings of endocrine toxicity related to combined anti CTLA-4 and anti-PD-1 therapy. Methods: We undertook a retrospective chart review of patients who received combined ipilimumab and nivolumab for metastatic melanoma at a tertiary referral centre between 2016-2019. We recorded onset and duration of abnormal biochemistry in endocrine irAEs, reviewed all available MRI images for pituitary size (mm) and appearance and 18-F FDG PET images for features of hypophysitis, thyroiditis and pancreatitis. Results: 162 patients received combination therapy. At least one irAE was recorded in 135 patients (83%), 100 (62%) required glucocorticoids, and 84 (52%) had an unplanned hospital presentation due to irAEs. Thyroiditis occurred in 50 (30.9%), with median time to onset of 30.9 days (range 1-234 days). 35 cases were identified with routine biochemistry performed every 4-6 weeks. TSH receptor antibody was measured in 13 patients and all were negative. 29 (58%) developed permanent hypothyroidism. Central cortisol deficiency was documented in 31 (19%) with a median time to diagnosis of 67.5 days (range 5-286). 4 cases were diagnosed on routine biochemistry and 14 presented with symptoms prompting investigation. 13 were diagnosed after routine neuroimaging demonstrated a pituitary abnormality, and a further 27 patients without the clinical syndrome had features of hypophysitis on neuroimaging. New onset diabetes occurred in 3 people, in which pancreatic inflammation on imaging was found in 2. A further 3/5 patients with an asymptomatic elevated lipase were found to have abnormal pancreatic imaging. In one patient with no features of endocrine or exocrine failure, there was a significant increase in FDG uptake and a subsequent loss of pancreatic volume. Conclusion: We report real world incidence of endocrine irAEs with combination immunotherapy. Routine biochemistry leads to the detection of some but not all cases. Early recognition and avoidance of unplanned presentations remains a challenge. Opportunistic assessment of endocrine gland appearance on routine imaging studies may provide useful early diagnostic information. Reference: Larkin J, Chiarion-Sileni V, Gonzalez R, Grob JJ, Cowey CL, Lao CD, et al. Combined nivolumab and ipilimumab or monotherapy in untreated melanoma. N Engl J Med. (2015) 1:23-34. 10.1056/NEJMoa1504030

FDG PET/CT for tumoral and systemic immune response monitoring of advanced melanoma during first-line combination ipilimumab and nivolumab treatment

PURPOSE

We aimed to investigate the role of FDG-PET/CT in monitoring of response and immune-related adverse events (irAEs) following first-line combination-immune checkpoint inhibitor (combination-ICI) therapy for advanced melanoma.

METHODS

We retrospectively reviewed outcomes in patients who had (1) first-line nivolumab plus ipilimumab; (2) pre- and post-treatment FDG-PET/CT scans (pre-FDG-PET/CT and post-FDG-PET/CT) within 2 and 4 months of starting ICI, respectively; and (3) at least one lesion assessable by PET response criteria in solid tumors (PERCIST). Extracranial response was monitored by 3 monthly FDG-PET/CT. Whole-body metabolic tumor volume (wbMTV) was measured pre- and post-treatment and correlated with outcome. FDG-PET/CT manifestations of irAE were defined as new increased non-tumoral uptake on post-FDG-PET/CT and were correlated with clinical presentation.

RESULTS

Thirty-one consecutive patients, median age 60 years (range, 30-78), were identified from 2016 to 2018. The median number of combination-ICI cycles to the first post-FDG-PET/CT response assessment was 3 (interquartile range (IQR), 2-4). The best-overall responses were complete metabolic response (CMR) in 25 (80%), partial metabolic response (PMR) in 3 (10%), and progressive metabolic disease (PMD) in 3 (10%) patients. Patients with PMD had significantly higher pre-treatment wbMTV (p = 0.009). At a median follow-up of 21.5 months, 26 (84%) patients were alive with median progression-free and overall survival not reached. Secondary progression occurred in 9/31 (29%) patients at a median of 8.2 months (IQR, 6.9-15.5), of those majority (78%) was detected by FDG-PET/CT. Of 36 findings on post-FDG-PET/CT suggestive of irAE, 29 (80%) had clinical confirmation. In 3 (7%), the FDG-PET/CT findings preceded clinical presentation. The most common FDG-PET/CT detectable irAEs were endocrinopathies (36%) and enterocolitis (35%).

CONCLUSION

FDG-PET/CT response evaluation predicts the long-term outcome of patients treated with first-line combination-ICIs. Long-term treatment response monitoring for detection of extracranial secondary progression is feasible by FDG-PET/CT. Beyond response assessment, FDG-PET/CT frequently detects clinically relevant irAEs, which may involve multiple systems contemporaneously or at various time-points and may precede clinical diagnosis.

i-Move, a personalised exercise intervention for patients with advanced melanoma receiving immunotherapy: a randomised feasibility trial protocol

INTRODUCTION

There is increasing evidence demonstrating the benefits of exercise in counteracting cancer treatment-related fatigue. Immunotherapy is an established treatment for advanced melanoma, and is associated with fatigue in a third of patients. The safety and efficacy of exercise in counteracting treatment-related fatigue in patients with advanced melanoma receiving immunotherapy are yet to be determined. This study aims to assess the safety, adherence to and acceptability of a mixed-methods parallel-group, pilot randomised controlled trial of a personalised, 12-week semi-supervised exercise programme prescribed by an exercise physiologist (iMove) in 30 patients with stage IV melanoma scheduled to commence immunotherapy: single agent ipilimumab, nivolumab or pembrolizumab, or combination ipilimumab and nivolumab. The trial will be used to provide preliminary evidence of the potential efficacy of exercise for managing fatigue.

METHODS AND ANALYSIS

Thirty participants will be recruited from a specialist cancer centre between May and September, 2019. Participants will be randomised 1:1 to receive iMove, or usual care (an information booklet about exercise for people with cancer). Feasibility data comprise: eligibility; recruitment and retention rates; adherence to and acceptability of exercise consultations, personalised exercise programme and study measures; and exercise-related adverse events. Patient-reported outcome measures assess potential impact of the exercise intervention on: fatigue, role functioning, symptoms and quality of life. Follow-up will comprise five time points over 24 weeks. Physical assessments measure physical fitness and functioning.

ETHICS AND DISSEMINATION

This study was reviewed and approved by the Peter MacCallum Cancer Centre Human Research Ethics Committee (HREC/48927/PMCC-2019). The findings from this trial will be disseminated via conference presentations and publications in peer-reviewed journals, and by engagement with clinicians, media, government and consumers. In particular, we will promote the outcomes of this work among the oncology community should this pilot indicate benefit for patients.

TRIAL REGISTRATION NUMBER

ACTRN12619000952145; Pre-results.

Clinical Utility of Real-Time Targeted Molecular Profiling in the Clinical Management of Ovarian Cancer: The ALLOCATE Study

PURPOSE

The ALLOCATE study was designed as a pilot to demonstrate the feasibility and clinical utility of real-time targeted molecular profiling of patients with recurrent or advanced ovarian cancer for identification of potential targeted therapies.

PATIENTS AND METHODS

A total of 113 patients with ovarian cancer of varying histologies were recruited from two tertiary hospitals, with 99 patient cases suitable for prospective analysis. Targeted molecular and methylation profiling of fresh biopsy and archived tumor samples were performed by screening for mutations or copy-number variations in 44 genes and for promoter methylation of BRCA1 and RAD51C.

RESULTS

Somatic genomic or methylation events were identified in 85% of all patient cases, with potentially actionable events with defined targeted therapies (including four resistance events) detected in 60% of all patient cases. On the basis of these findings, six patients received molecularly guided therapy, three patients had unsuspected germline cancer–associated BRCA1/ 2 mutations and were referred for genetic counseling, and two intermediate differentiated (grade 2) serous ovarian carcinomas were reclassified as low grade, leading to changes in clinical management. Additionally, secondary reversion mutations in BRCA1/ 2 were identified in fresh biopsy samples of two patients, consistent with clinical platinum/poly (ADP-ribose) polymerase inhibitor resistance. Timely reporting of results if molecular testing is done at disease recurrence, as well as early referral for patients with platinum-resistant cancers, were identified as factors that could improve the clinical utility of molecular profiling.

CONCLUSION

ALLOCATE molecular profiling identified known genomic and methylation alterations of the different ovarian cancer subtypes and was deemed feasible and useful in routine clinical practice. Better patient selection and access to a wider range of targeted therapies or clinical trials will further enhance the clinical utility of molecular profiling.

The molecular origin and taxonomy of mucinous ovarian carcinoma

Mucinous ovarian carcinoma (MOC) is a unique subtype of ovarian cancer with an uncertain etiology, including whether it genuinely arises at the ovary or is metastatic disease from other organs. In addition, the molecular drivers of invasive progression, high-grade and metastatic disease are poorly defined. We perform genetic analysis of MOC across all histological grades, including benign and borderline mucinous ovarian tumors, and compare these to tumors from other potential extra-ovarian sites of origin. Here we show that MOC is distinct from tumors from other sites and supports a progressive model of evolution from borderline precursors to high-grade invasive MOC. Key drivers of progression identified are TP53 mutation and copy number aberrations, including a notable amplicon on 9p13. High copy number aberration burden is associated with worse prognosis in MOC. Our data conclusively demonstrate that MOC arise from benign and borderline precursors at the ovary and are not extra-ovarian metastases.

Clinical and FDG-PET markers of immune checkpoint inhibitor (ICI) response in patients with metastatic Merkel cell carcinoma (mMCC)

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Background: mMCC is a rare, highly aggressive neuroendocrine cancer with a poor prognosis. ICIs have favourable efficacy and safety in clinical trials. We outline single centre experience utilising ICIs in mMCC. Methods: Medical records of patients (pts) with mMCC treated with ICIs from Aug 2015 to Dec 2018 at Peter MacCallum Cancer Centre in Australia were retrospectively analysed. RNA sequencing and immunohistochemistry for PD-L1, CD3 and Merkel cell polyomavirus (MCPyV) on tumor samples were performed. Baseline tumor volumes and responses were assessed with FDG-PET scans using the Hicks criteria. Results: 23 pts with mMCC were treated with ICIs. Pt characteristics are summarised in Table. A median of 8 cycles (range 1 to 47) were administered, with treatment ongoing in 7 pts. Objective responses (OR) were observed in 14 pts (61%); 10 (44%) complete metabolic responses (CMR) and 4 (17%) partial metabolic responses (PMR). Median time to response was 9 weeks (range 4 to 11) and 12-month progression-free survival (PFS) rate was 32%. Increased OR were seen in pts aged less than 75 (OR 8/10, 80% vs 46%), no prior history of chemotherapy (OR 10/14, 71% vs 44%), pts with an immune-related adverse event (irAE) (OR 6/6, 100% vs 47%) and in MCPyV negative pts (OR 9/11, 82% vs 50%). Pts with a CMR had lower mean-tumor volume on baseline FDG-PET scan (CMR: 35.7mL, no CMR: 187.8mL, p value 0.05). 10 pts received radiation (RT) during ICI: 4 pts started RT concurrently (OR 75%, CMR 50%), 3 pts had isolated ICI-resistant lesions successfully treated with RT and 3 pts with multisite progression continued to progress despite RT. 6 pts (26%) had a Grade 1-2 irAE. Conclusions: ICIs showed efficacy and safety consistent with trial data. Younger age, negative MCPyV status, no prior chemotherapy, lower baseline FDG-PET tumor volume and irAEs are potentially associated with better responses. [Table: see text]

Efficacy of immune checkpoint inhibitors (ICIs) for in-transit melanoma

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Background: The efficacy of ICIs in metastatic melanoma is well-established. However, there is limited data regarding their efficacy in in-transit melanoma metastases (ITM). This study assessed the efficacy of ICI in patients with ITM. Methods: A multisite, retrospective review of patients with ITM treated with ICI from 2004-2018. Demographic and clinicopathological factors (age, sex, primary site, AJCC version 8 stage, BRAF status, prior locoregional therapies) were collected. Objective response rate (ORR) based on a clinician-assessed best overall response, progression free survival (PFS) and overall survival (OS) were analyzed by the Kaplan-Meier method. Results: Fifty-four patients were included: 27 (50%) female; median age 69 (range 19-89); 12 (22%) stage IIIB, 40 (74%) stage IIIC and 2 (4%) stage IIID; 10(19%) BRAF mutant. Forty (74%) received single agent PD-1 inhibitor (pembrolizumab or nivolumab), 8 (15%) single agent anti-CTLA-4 (ipilimumab), 5 (9%) combination anti-PD-1/anti-CTLA-4 (ipilimumab and nivolumab or pembrolizumab) and 1 (2%) combination anti-PDL-1/MEK inhibitor (atezolizumab and cobimetinib). ORR to ICI was 54%: 14 (26%) complete responses; 15 (28%) partial responses; 9 (17%) stable disease; 16 (30%) progressive disease. Thirteen (46%) responders had only one ITM lesion. ORR was 58% for single agent anti PD-1, 38% for single agent anti-CTLA4, and 40% for anti-PD-1/anti-CTLA-4 (Table). The median follow-up was 15 months (2-46). The median PFS was 11.7 months (6.6-N/A). PFS at 1 and 2 years were 48% and 39%. Fourteen (56%) progressed locoregionally and 11 (44%) progressed distantly. OS at 1 and 2 years were 85% and 63%; the median OS was not reached. No clinicopathological features were associated with ORR. Conclusions: ICI produces objective responses in ITM and should be considered in patients with unresectable ITM or disease recurrence despite locoregional therapies. [Table: see text]

19q12 amplified and non-amplified subsets of high grade serous ovarian cancer with overexpression of cyclin E1 differ in their molecular drivers and clinical outcomes

OBJECTIVES

Readily apparent cyclin E1 expression occurs in 50% of HGSOC, but only half are linked to 19q12 locus amplification. The amplified/cyclin E1^hi subset has intact BRCA1/2, unfavorable outcome, and is potentially therapeutically targetable. We studied whether non-amplified/cyclin E1^hi HGSOC has similar characteristics. We also assessed the expression of cyclin E1 degradation-associated proteins, FBXW7 and USP28, as potential drivers of high cyclin E1 expression in both subsets.

METHODS

262 HGSOC cases were analyzed by in situ hybridization for 19q12 locus amplification and immunohistochemistry for cyclin E1, URI1 (another protein encoded by the 19q12 locus), FBXW7 and USP28 expression. Tumors were classified by 19q12 amplification status and correlated to cyclin E1 and URI1 expression, BRCA1/2 germline mutation, FBXW7 and USP28 expression, and clinical outcomes. Additionally, we assessed the relative genomic instability of amplified/cyclin E1^hi and non-amplified/cyclin E1^hi groups of HGSOC datasets from The Cancer Genome Atlas.

RESULTS

Of the 82 cyclin E1^hi cases, 43 (52%) were amplified and 39 (48%) were non-amplified. Unlike amplified tumors, non-amplified/cyclin E1^hi tumor status was not mutually exclusive with gBRCA1/2 mutation. The non-amplified/cyclin E1^hi group had significantly increased USP28, while the amplified/cyclin E1^hi cancers had significantly lower FBXW7 expression consistent with a role for both in stabilizing cyclin E1. Notably, only the amplified/cyclin E1^hi subset was associated with genomic instability and had a worse outcome than non-amplified/cyclin E1^hi group.

CONCLUSIONS

Amplified/cyclin E1^hi and non-amplified/cyclin E1^hi tumors have different pathological and biological characteristics and clinical outcomes indicating that they are separate subsets of cyclin E1^hi HGSOC.

Abstract B35: Australian Ovarian Cancer Assortment Trial–Allocating ovarian cancer patients into clinical trials based on molecular profiling

Background: The Australian Ovarian Cancer Assortment Trial (ALLOCATE) was designed as a pilot study to demonstrate feasibility of molecularly profiling patients with recurrent ovarian cancer with the aim of allocating patients to targeted therapies based on the genomic profile of their tumors.

Materials and Methods: Two next-generation sequencing (NGS) panels, as well as a BRCA1 methylation assay, were used for molecular profiling of most common subtypes of ovarian cancer. A custom Illumina TruSeq Amplicon Low Input (v2) panel with dual-strand coverage was designed to target 38 genes commonly mutated and clinically important in ovarian cancer. The second assay was a NGS modification of the Multiplex Ligation-dependent Probe Amplification (MLPA) assay that was designed to target 11 genes with common copy number alterations (CNA) in ovarian cancer, including extensive BRCA1/2 coverage for large exonic deletions (Kondrashova et al., 2015). A thorough analytic validation was performed to ensure that both tests were fit for diagnostic use.

Patients with recurrent epithelial ovarian cancer were eligible for the study. Where feasible, patients underwent biopsies of recurrent tumor that were snap frozen. Otherwise, archival FFPE tumor blocks were retrieved. Sequencing was performed using Illumina Miseq and HiSeq 2500 with target median coverage of 2000x (amplicon panel) and 800x (MLPA-Seq). Data were analyzed using an internally built pipeline, an upgraded version of AmpliVar (Hsu et al 2015), with Variant Effect Predictor (Mclaren et al., 2016) used for variant annotation.

Results: Between December 2013 and October 2016, 113 patients with recurrent ovarian cancer were recruited from two tertiary hospitals, with 15 cases (13%) excluded due to insufficient tumor material or poor-quality DNA. Ninety-eight cases (87%) were analyzed and reports issued back to the referring clinician.

Fifty-six patients (61%) in the study had recurrent high-grade serous ovarian cancer (HGSC). Of these, TP53 mutations were identified in 91%. Events in genes other than TP53 were detected in 44 cases, most commonly MYC and CCNE1 amplifications and BRCA1/2 mutations. BRCA1/2 reversions were identified in two cases, explaining their lack of response to platinum/PARPi.

Fifteen patients (16%) had recurrent low-grade serous ovarian cancer (LGSC), with KRAS or BRAF mutations identified in four cases. Two HGSC tumors were reclassified as LGSC on the basis of a lack of TP53 mutation, presence of KRAS mutation, and subsequent pathology review. Other cases in the study included mucinous, clear cell, and mixed-histology carcinomas and a metastatic carcinosarcoma.

In terms of clinical utility, 6 patients (7%) received a matched therapy. Three HGSC patients with somatic BRCA1/2 mutations were treated with PARP inhibitors. Another HGSC patient with ERBB2 amplification was treated with trastuzumab. One LGSC patient with a BRAF mutation was enrolled on a BRAF inhibitor clinical trial. A second LGSC patient was enrolled in a trial of anastrazole. Furthermore, 7 patients (14%) with HGSC who were previously untested were found to have a germline BRCA1/2 mutation and were subsequently referred to a familial cancer clinic for further management and cascade testing.

The limitations in the study included the turnaround time and advanced stage of disease at enrolment, which significantly affected the clinical utility of the test.

Conclusion: We demonstrated that molecular profiling of recurrent ovarian cancer using the ALLOCATE panel was feasible and reflected the known genomic characteristics of the different subtypes. However, challenges remain, including appropriate patient selection and efficient turnaround time for reporting. Furthermore, improved access to targeted therapies or clinical trials will also enhance the clinical utility of the ALLOCATE panel.

Citation Format: Olga Kondrashova, George Au-Yeung, Leakhena Leas, Gwo-Yaw Ho, Sebastian Lunke, Kathryn Alsop, Clare Scott, Anne Hamilton, Sumitra Ananda, Alison Freimund, Michael Quinn, Orla McNally, Nadia Traficante, Tiffany Cowie, Matthew Wakefield, Arthur Hsu, Alex Dobrovic, Michael Christie, Graham Taylor, David Bowtell, Linda Mileshkin, Paul Waring. Australian Ovarian Cancer Assortment Trial–Allocating ovarian cancer patients into clinical trials based on molecular profiling. [abstract]. In: Proceedings of the AACR Conference: Addressing Critical Questions in Ovarian Cancer Research and Treatment; Oct 1-4, 2017; Pittsburgh, PA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(15_Suppl):Abstract nr B35.

EIF1AX and NRAS Mutations Co-occur and Cooperate in Low-Grade Serous Ovarian Carcinomas

Low-grade serous ovarian carcinomas (LGSC) are associated with a poor response to chemotherapy and are molecularly characterized by RAS pathway activation. Using exome and whole genome sequencing, we identified recurrent mutations in the protein translational regulator EIF1AX and in NF1, USP9X, KRAS, BRAF, and NRAS RAS pathway mutations were mutually exclusive; however, we found significant co-occurrence of mutations in NRAS and EIF1AX Missense EIF1AX mutations were clustered at the N-terminus of the protein in a region associated with its role in ensuring translational initiation fidelity. Coexpression of mutant NRAS and EIF1AX proteins promoted proliferation and clonogenic survival in LGSC cells, providing the first example of co-occurring, growth-promoting mutational events in ovarian cancer. Cancer Res; 77(16); 4268-78. ©2017 AACR.

Selective Targeting of Cyclin E1-Amplified High-Grade Serous Ovarian Cancer by Cyclin-Dependent Kinase 2 and AKT Inhibition

Purpose: Cyclin E1 (CCNE1) amplification is associated with primary treatment resistance and poor outcome in high-grade serous ovarian cancer (HGSC). Here, we explore approaches to target CCNE1-amplified cancers and potential strategies to overcome resistance to targeted agents.Experimental Design: To examine dependency on CDK2 in CCNE1-amplified HGSC, we utilized siRNA and conditional shRNA gene suppression, and chemical inhibition using dinaciclib, a small-molecule CDK2 inhibitor. High-throughput compound screening was used to identify selective synergistic drug combinations, as well as combinations that may overcome drug resistance. An observed relationship between CCNE1 and the AKT pathway was further explored in genomic data from primary tumors, and functional studies in fallopian tube secretory cells.Results: We validate CDK2 as a therapeutic target by demonstrating selective sensitivity to gene suppression. However, we found that dinaciclib did not trigger amplicon-dependent sensitivity in a panel of HGSC cell lines. A high-throughput compound screen identified synergistic combinations in CCNE1-amplified HGSC, including dinaciclib and AKT inhibitors. Analysis of genomic data from TCGA demonstrated coamplification of CCNE1 and AKT2 Overexpression of Cyclin E1 and AKT isoforms, in addition to mutant TP53, imparted malignant characteristics in untransformed fallopian tube secretory cells, the dominant site of origin of HGSC.Conclusions: These findings suggest a specific dependency of CCNE1-amplified tumors for AKT activity, and point to a novel combination of dinaciclib and AKT inhibitors that may selectively target patients with CCNE1-amplified HGSC. Clin Cancer Res; 23(7); 1862-74. ©2016 AACR.

Whole-genome characterization of chemoresistant ovarian cancer

Patients with high-grade serous ovarian cancer (HGSC) have experienced little improvement in overall survival, and standard treatment has not advanced beyond platinum-based combination chemotherapy, during the past 30 years. To understand the drivers of clinical phenotypes better, here we use whole-genome sequencing of tumour and germline DNA samples from 92 patients with primary refractory, resistant, sensitive and matched acquired resistant disease. We show that gene breakage commonly inactivates the tumour suppressors RB1, NF1, RAD51B and PTEN in HGSC, and contributes to acquired chemotherapy resistance. CCNE1 amplification was common in primary resistant and refractory disease. We observed several molecular events associated with acquired resistance, including multiple independent reversions of germline BRCA1 or BRCA2 mutations in individual patients, loss of BRCA1 promoter methylation, an alteration in molecular subtype, and recurrent promoter fusion associated with overexpression of the drug efflux pump MDR1.

Whole-genome characterization of chemoresistant ovarian cancer

Patients with high-grade serous ovarian cancer (HGSC) have experienced little improvement in overall survival, and standard treatment has not advanced beyond platinum-based combination chemotherapy, during the past 30 years. To understand the drivers of clinical phenotypes better, here we use whole-genome sequencing of tumour and germline DNA samples from 92 patients with primary refractory, resistant, sensitive and matched acquired resistant disease. We show that gene breakage commonly inactivates the tumour suppressors RB1, NF1, RAD51B and PTEN in HGSC, and contributes to acquired chemotherapy resistance. CCNE1 amplification was common in primary resistant and refractory disease. We observed several molecular events associated with acquired resistance, including multiple independent reversions of germline BRCA1 or BRCA2 mutations in individual patients, loss of BRCA1 promoter methylation, an alteration in molecular subtype, and recurrent promoter fusion associated with overexpression of the drug efflux pump MDR1.

Resistance to CDK2 inhibitors is associated with selection of polyploid cells in CCNE1-amplified ovarian cancer

PURPOSE

Amplification of cyclin E1 (CCNE1) is associated with poor outcome in breast, lung, and other solid cancers, and is the most prominent structural variant associated with primary treatment failure in high-grade serous ovarian cancer (HGSC). We have previously shown that CCNE1-amplified tumors show amplicon-dependent sensitivity to CCNE1 suppression. Here, we explore targeting CDK2 as a novel therapeutic strategy in CCNE1-amplified cancers and mechanisms of resistance.

EXPERIMENTAL DESIGN

We examined the effect of CDK2 suppression using RNA interference and small-molecule inhibitors in SK-OV-3, OVCAR-4, and OVCAR-3 ovarian cancer cell lines. To identify mechanisms of resistance, we derived multiple, independent resistant sublines of OVCAR-3 to CDK2 inhibitors. Resistant cells were extensively characterized by gene expression and copy number analysis, fluorescence-activated cell sorting profiling and conventional karyotyping. In addition, we explored the relationship between CCNE1 amplification and polyploidy using data from primary tumors.

RESULTS

We validate CDK2 as a therapeutic target in CCNE1-amplified cells by showing selective sensitivity to suppression, either by gene knockdown or using small-molecule inhibitors. In addition, we identified two resistance mechanisms, one involving upregulation of CDK2 and another novel mechanism involving selection of polyploid cells from the pretreatment tumor population. Our analysis of genomic data shows that polyploidy is a feature of cancer genomes with CCNE1 amplification.

CONCLUSIONS

These findings suggest that cyclinE1/CDK2 is an important therapeutic target in HGSC, but that resistance to CDK2 inhibitors may emerge due to upregulation of CDK2 target protein and through preexisting cellular polyploidy.

Radiation with cisplatin or carboplatin for locally advanced cervix cancer: The experience of a tertiary cancer center

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Background: Definitive treatment with concurrent cisplatin and radiation is the standard of care for locally advanced cervical cancer. The optimal management of patients with a contraindication to cisplatin has not been established. We conducted a retrospective audit of the impact of concurrent chemoradiation in a cohort of patients (pts) with locally advanced cervical cancer. Methods: All pts with locally advanced cervical cancer treated with definitive radiation were entered into a prospective database. Information regarding their demographics, stage, histology, recurrence and survival were recorded. Pharmacy records were reviewed to determine concurrent chemotherapy use. The primary endpoint was overall survival, and secondary endpoints were disease free survival and rates of primary, nodal or distant failure. Univariate and multivariate analyses were performed, incorporating known prognostic factors of age, FIGO stage, uterine body involvement, tumour volume on MRI and nodal involvement. Results: 442 pts were treated from Jan 1996 to Feb 2011. Median age was 59 (range 22-94); 89% had squamous histology and 64% node-negative disease. 269 pts received cisplatin, 59 received carboplatin because of a contraindication to cisplatin and 114 received no concurrent chemotherapy (most prior to 1999). Overall survival adjusted for other prognostic factors was significantly improved with use of concurrent cisplatin compared to radiation alone (HR 0.53, p=0.001), as was disease free survival and the rate of distant failure. Use of concurrent carboplatin was not associated with any significant benefit compared to radiation alone in terms of overall survival or disease free survival on univariate or multivariate analyses. Conclusions: The results of this audit are consistent with the known significant survival benefit with concurrent cisplatin chemoradiation. However, there did not appear to be any significant benefit associated with concurrent carboplatin although there are potential confounding factors in this small cohort. The available evidence in the literature favors the use of non-platinum chemotherapy rather than carboplatin in pts with contraindications to cisplatin.