Hussein Abdul-Hassan Tawbi

Gut microbiome modulates response to anti-PD-1 immunotherapy in melanoma patients.

Good bacteria help fight cancer Resident gut bacteria can affect patient responses to cancer immunotherapy (see the Perspective by Jobin). Routy et al. show that antibiotic consumption is associated with poor response to immunotherapeutic PD-1 blockade. They profiled samples from patients with lung and kidney cancers and found that nonresponding patients had low levels of the bacterium Akkermansia muciniphila. Oral supplementation of the bacteria to antibiotic-treated mice restored the response to immunotherapy. Matson et al. and Gopalakrishnan et al. studied melanoma patients receiving PD-1 blockade and found a greater abundance of “good” bacteria in the guts of responding patients. Nonresponders had an imbalance in gut flora composition, which correlated with impaired immune cell activity. Thus, maintaining healthy gut flora could help patients combat cancer. Science, this issue p. 91, p. 104, p. 97; see also p. 32 Gut bacteria influence patient response to cancer therapy. Preclinical mouse models suggest that the gut microbiome modulates tumor response to checkpoint blockade immunotherapy; however, this has not been well-characterized in human cancer patients. Here we examined the oral and gut microbiome of melanoma patients undergoing anti–programmed cell death 1 protein (PD-1) immunotherapy (n = 112). Significant differences were observed in the diversity and composition of the patient gut microbiome of responders versus nonresponders. Analysis of patient fecal microbiome samples (n = 43, 30 responders, 13 nonresponders) showed significantly higher alpha diversity (P < 0.01) and relative abundance of bacteria of the Ruminococcaceae family (P < 0.01) in responding patients. Metagenomic studies revealed functional differences in gut bacteria in responders, including enrichment of anabolic pathways. Immune profiling suggested enhanced systemic and antitumor immunity in responding patients with a favorable gut microbiome as well as in germ-free mice receiving fecal transplants from responding patients. Together, these data have important implications for the treatment of melanoma patients with immune checkpoint inhibitors.

Integrated molecular analysis of tumor biopsies on sequential CTLA-4 and PD-1 blockade reveals markers of response and resistance

Profiling of melanoma patients treated with checkpoint blockade reveals TCR clonality and copy number loss as correlates of therapeutic response. Checking on checkpoint inhibitors Immune checkpoint blockade has greatly improved the success of treatment in melanoma and other tumor types, but it is expensive and does not work for all patients. To optimize the likelihood of therapeutic success and reduce the risks and expense of unnecessary treatment, it would be helpful to find biomarkers that can predict treatment response. Roh et al. studied patients treated with sequential checkpoint inhibitors targeting CTLA-4 and then PD-1. In these patients, the authors discovered that a more clonal T cell population specifically correlates with response to PD-1 blockade, but not CTLA-4, which may help identify the best candidates for this treatment. In addition, increased frequency of gene copy number loss was correlated with decreased responsiveness to either therapy. Immune checkpoint blockade produces clinical benefit in many patients. However, better biomarkers of response are still needed, and mechanisms of resistance remain incompletely understood. To address this, we recently studied a cohort of melanoma patients treated with sequential checkpoint blockade against cytotoxic T lymphocyte antigen–4 (CTLA-4) followed by programmed death receptor–1 (PD-1) and identified immune markers of response and resistance. Building on these studies, we performed deep molecular profiling including T cell receptor sequencing and whole-exome sequencing within the same cohort and demonstrated that a more clonal T cell repertoire was predictive of response to PD-1 but not CTLA-4 blockade. Analysis of CNAs identified a higher burden of copy number loss in nonresponders to CTLA-4 and PD-1 blockade and found that it was associated with decreased expression of genes in immune-related pathways. The effect of mutational load and burden of copy number loss on response was nonredundant, suggesting the potential utility of a combinatorial biomarker to optimize patient care with checkpoint blockade therapy.

Role of PARP Inhibitors in Cancer Biology and Therapy

Deeper understanding of DNA repair mechanisms and their potential value as therapeutic targets in oncology heralded the clinical development of poly(ADP-ribose) polymerase (PARP) inhibitors. Although initially developed to exploit synthetic lethality in models of cancer associated with defective DNA repair, our burgeoning knowledge of PARP biology has resulted in these agents being exploited both in cancer with select chemotherapeutic agents and in non-malignant diseases. In this review article, we briefly review the mechanisms of DNA repair and pre-clinical development of PARP inhibitors before discussing the clinical development of the various PARP inhibitors in depth.

Pembrolizumab in advanced soft-tissue sarcoma and bone sarcoma (SARC028): a multicentre, two-cohort, single-arm, open-label, phase 2 trial

BACKGROUNDnPatients with advanced sarcomas have a poor prognosis and few treatment options that improve overall survival. Chemotherapy and targeted therapies offer short-lived disease control. We assessed pembrolizumab, an anti-PD-1 antibody, for safety and activity in patients with advanced soft-tissue sarcoma or bone sarcoma.nnnMETHODSnIn this two-cohort, single-arm, open-label, phase 2 study, we enrolled patients with soft-tissue sarcoma or bone sarcoma from 12 academic centres in the USA that were members of the Sarcoma Alliance for Research through Collaboration (SARC). Patients with soft-tissue sarcoma had to be aged 18 years or older to enrol; patients with bone sarcoma could enrol if they were aged 12 years or older. Patients had histological evidence of metastatic or surgically unresectable locally advanced sarcoma, had received up to three previous lines of systemic anticancer therapy, had at least one measurable lesion according to the Response Evaluation Criteria In Solid Tumors version 1.1, and had at least one lesion accessible for biopsy. All patients were treated with 200 mg intravenous pembrolizumab every 3 weeks. The primary endpoint was investigator-assessed objective response. Patients who received at least one dose of pembrolizumab were included in the safety analysis and patients who progressed or reached at least one scan assessment were included in the activity analysis. Accrual is ongoing in some disease cohorts. This trial is registered with ClinicalTrials.gov, number NCT02301039.nnnFINDINGSnBetween March 13, 2015, and Feb 18, 2016, we enrolled 86 patients, 84 of whom received pembrolizumab (42 in each disease cohort) and 80 of whom were evaluable for response (40 in each disease cohort). Median follow-up was 17·8 months (IQR 12·3-19·3). Seven (18%) of 40 patients with soft-tissue sarcoma had an objective response, including four (40%) of ten patients with undifferentiated pleomorphic sarcoma, two (20%) of ten patients with liposarcoma, and one (10%) of ten patients with synovial sarcoma. No patients with leiomyosarcoma (n=10) had an objective response. Two (5%) of 40 patients with bone sarcoma had an objective response, including one (5%) of 22 patients with osteosarcoma and one (20%) of five patients with chondrosarcoma. None of the 13 patients with Ewings sarcoma had an objective response. The most frequent grade 3 or worse adverse events were anaemia (six [14%]), decreased lymphocyte count (five [12%]), prolonged activated partial thromboplastin time (four [10%]), and decreased platelet count (three [7%]) in the bone sarcoma group, and anaemia, decreased lymphocyte count, and prolonged activated partial thromboplastin time in the soft-tissue sarcoma group (three [7%] each). Nine (11%) patients (five [12%] in the bone sarcoma group and four [10%] in the soft-tissue sarcoma group) had treatment-emergent serious adverse events (SAEs), five of whom had immune-related SAEs, including two with adrenal insufficiency, two with pneumonitis, and one with nephritis.nnnINTERPRETATIONnThe primary endpoint of overall response was not met for either cohort. However, pembrolizumab showed encouraging activity in patients with undifferentiated pleomorphic sarcoma or dedifferentiated liposarcoma. Enrolment to expanded cohorts of those subtypes is ongoing to confirm and characterise the activity of pembrolizumab.nnnFUNDINGnMerck, SARC, Sarcoma Foundation of America, QuadW Foundation, Pittsburgh Cure Sarcoma, and Ewan McGregor.

Neoadjuvant plus adjuvant dabrafenib and trametinib versus standard of care in patients with high-risk, surgically resectable melanoma: a single-centre, open-label, randomised, phase 2 trial

BACKGROUNDnDual BRAF and MEK inhibition produces a response in a large number of patients with stage IV BRAF-mutant melanoma. The existing standard of care for patients with clinical stage III melanoma is upfront surgery and consideration for adjuvant therapy, which is insufficient to cure most patients. Neoadjuvant targeted therapy with BRAF and MEK inhibitors (such as dabrafenib and trametinib) might provide clinical benefit in this high-risk p opulation.nnnMETHODSnWe undertook this single-centre, open-label, randomised phase 2 trial at the University of Texas MD Anderson Cancer Center (Houston, TX, USA). Eligible participants were adult patients (aged ≥18 years) with histologically or cytologically confirmed surgically resectable clinical stage III or oligometastatic stage IV BRAFV600E or BRAFV600K (ie, Val600Glu or Val600Lys)-mutated melanoma. Eligible patients had to have an Eastern Cooperative Oncology Group performance status of 0 or 1, a life expectancy of more than 3 years, and no previous exposure to BRAF or MEK inhibitors. Exclusion criteria included metastases to bone, brain, or other sites where complete surgical excision was in doubt. We randomly assigned patients (1:2) to either upfront surgery and consideration for adjuvant therapy (standard of care group) or neoadjuvant plus adjuvant dabrafenib and trametinib (8 weeks of neoadjuvant oral dabrafenib 150 mg twice per day and oral trametinib 2 mg per day followed by surgery, then up to 44 weeks of adjuvant dabrafenib plus trametinib starting 1 week after surgery for a total of 52 weeks of treatment). Randomisation was not masked and was implemented by the clinical trial conduct website maintained by the trial centre. Patients were stratified by disease stage. The primary endpoint was investigator-assessed event-free survival (ie, patients who were alive without disease progression) at 12 months in the intent-to-treat population. This trial is registered at ClinicalTrials.gov, number NCT02231775.nnnFINDINGSnBetween Oct 23, 2014, and April 13, 2016, we randomly assigned seven patients to standard of care, and 14 to neoadjuvant plus adjuvant dabrafenib and trametinib. The trial was stopped early after a prespecified interim safety analysis that occurred after a quarter of the participants had been accrued revealed significantly longer event-free survival with neoadjuvant plus adjuvant dabrafenib and trametinib than with standard of care. After a median follow-up of 18·6 months (IQR 14·6-23·1), significantly more patients receiving neoadjuvant plus adjuvant dabrafenib and trametinib were alive without disease progression than those receiving standard of care (ten [71%] of 14 patients vs none of seven in the standard of care group; median event-free survival was 19·7 months [16·2-not estimable] vs 2·9 months [95% CI 1·7-not estimable]; hazard ratio 0·016, 95% CI 0·00012-0·14, p<0·0001). Neoadjuvant plus adjuvant dabrafenib and trametinib were well tolerated with no occurrence of grade 4 adverse events or treatment-related deaths. The most common adverse events in the neoadjuvant plus adjuvant dabrafenib and trametinib group were expected grade 1-2 toxicities including chills (12 patients [92%]), headache (12 [92%]), and pyrexia (ten [77%]). The most common grade 3 adverse event was diarrhoea (two patients [15%]).nnnINTERPRETATIONnNeoadjuvant plus adjuvant dabrafenib and trametinib significantly improved event-free survival versus standard of care in patients with high-risk, surgically resectable, clinical stage III-IV melanoma. Although the trial finished early, limiting generalisability of the results, the findings provide proof-of-concept and support the rationale for further investigation of neoadjuvant approaches in this disease. This trial is currently continuing accrual as a single-arm study of neoadjuvant plus adjuvant dabrafenib and trametinib.nnnFUNDINGnNovartis Pharmaceuticals Corporation.

Radiation necrosis with stereotactic radiosurgery combined with CTLA-4 blockade and PD-1 inhibition for treatment of intracranial disease in metastatic melanoma

Immune checkpoint inhibitors have demonstrated remarkable benefits in cancer patients. However, concern regarding toxicity in the setting of stereotactic radiosurgery (SRS) is often raised. In this study, we characterize radiation necrosis (RN) following immunotherapy and SRS. Melanoma patients treated with SRS and anti-CTLA-4 and/or anti-PD-1 at our institution from January 2006 to December 2015 were retrospectively reviewed. Overall survival (OS) and time to RN were assessed using Kaplan–Meier analysis. Logistic regression and Cox proportional hazards analyses were performed to identify predictors of radiation necrosis-free survival (RNFS) and RN risk. One-hundred thirty-seven patients with 1094 treated lesions over 296 SRS sessions were analyzed. Median follow-up was 9.8xa0months from SRS. Rate of RN was 27% of patients with median time to RN of 6xa0months. Median OS from SRS treatment was 16.9xa0months. RNFS at 6xa0months, 1 and 2xa0years was 92.7, 83.0, and 81.2%. Treatment with chemotherapy within 6xa0months of SRS was associated with worse RNFS at 1xa0year (78.4 vs. 87.5%, pu2009=u20090.017). On multivariate analysis, chemotherapy within 6xa0months and increased number of lesions treated were predictive of increased RN risk (HR 2.20, 95% CI 1.22–3.97, pu2009=u20090.009; HR 1.09, 95% CI 1.03–1.15, pu2009=u20090.002), whereas immunotherapy type and targeted therapy were not predictive. Median target volume of lesions that developed RN was greater than that of lesions that did not (pu2009<u20090.001). Concurrent treatment with chemotherapy, larger size and number of lesions treated were predictive of RN. Immunotherapy type and timing proximity to SRS were not associated with RN risk.

Genomic and immune heterogeneity are associated with differential responses to therapy in melanoma

Appreciation for genomic and immune heterogeneity in cancer has grown though the relationship of these factors to treatment response has not been thoroughly elucidated. To better understand this, we studied a large cohort of melanoma patients treated with targeted therapy or immune checkpoint blockade (nu2009=u200960). Heterogeneity in therapeutic responses via radiologic assessment was observed in the majority of patients. Synchronous melanoma metastases were analyzed via deep genomic and immune profiling, and revealed substantial genomic and immune heterogeneity in all patients studied, with considerable diversity in T cell frequency, and few shared T cell clones (<8% on average) across the cohort. Variables related to treatment response were identified via these approaches and through novel radiomic assessment. These data yield insight into differential therapeutic responses to targeted therapy and immune checkpoint blockade in melanoma, and have key translational implications in the age of precision medicine.Melanoma: Tumor differences within a patient may explain heterogeneous responsesPatients with metastatic melanoma display molecular and immune differences across tumor sites associated with differential drug responses. A team led by Jennifer Wargo from the University of Texas MD Anderson Cancer Center, Houston, USA, studied the radiological responses of 60 patients with metastatic melanoma, half of whom received targeted drug therapy and half of whom received an immune checkpoint inhibitor. The majority (83%) showed differences in responses across metastases. The group then profiled tumors in a subset, and found molecular and immune heterogeneity in different tumors within the same patient. Heterogeneity in mutational and immune profiles within tumors from individual patients could explain differences in treatment response. Knowing this, the authors emphasize the importance of acquiring biopsies from more than one tumor site in order to best tailor therapies to the features of metastatic cancer.

Phase 2 study of dasatinib in patients with alveolar soft part sarcoma, chondrosarcoma, chordoma, epithelioid sarcoma, or solitary fibrous tumor

Alveolar soft part sarcoma (ASPS), chondrosarcoma (CS), chordoma, epithelioid sarcoma, and solitary fibrous tumor (SFT) are malignant tumors that are relatively resistant to chemotherapy and for which more effective drug therapy is needed.

MicroRNA‐125a promotes resistance to BRAF inhibitors through suppression of the intrinsic apoptotic pathway

Melanoma patients with BRAFV600E‐mutant tumors display striking responses to BRAF inhibitors (BRAFi); however, almost all invariably relapse with drug‐resistant disease. Here, we report that microRNA‐125a (miR‐125a) expression is upregulated in human melanoma cells and patient tissues upon acquisition of BRAFi resistance. We show that miR‐125a induction confers resistance to BRAFV600E melanoma cells to BRAFi by directly suppressing pro‐apoptotic components of the intrinsic apoptosis pathway, including BAK1 and MLK3. Apoptotic suppression and prolonged survival favor reactivation of the MAPK and AKT pathways by drug‐resistant melanoma cells. We demonstrate that miR‐125a inhibition suppresses the emergence of resistance to BRAFi and, in a subset of resistant melanoma cell lines, leads to partial drug resensitization. Finally, we show that miR‐125a upregulation is mediated by TGFβ signaling. In conclusion, the identification of this novel role for miR‐125a in BRAFi resistance exposes clinically relevant mechanisms of melanoma cell survival that can be exploited therapeutically.

Abstract PD09-06: Two phase I trials exploring different dosing schedules of carboplatin (C), paclitaxel (P), and the poly-ADP-ribose polymerase (PARP) inhibitor, veliparib (ABT-888) (V) with activity in triple negative breast cancer (TNBC)

Background: The histopathologic and molecular similarities between TNBC and BRCA-1 mutation related breast cancer provide rationale for the use of PARP inhibitors in treating sporadic TNBC. C and P are established drugs in the treatment of advanced breast cancer. In order to determine the recommend phase II dose (RP2D) of V in combination with C and P, two separate phase I trials evaluated the combination of V with C and P dosed weekly (q1wk) and every 3 weeks (q3wk). Methods: Both phase I trials were a standard 3+3 dose escalation design of C, P, and V open to patients (pts) with advanced solid tumors and enriched for pts with TNBC. In the q1wk trial, C was given weekly on day 3 at an AUC of 2, P was given weekly on day 3 at a dose of 80 mg/m 2 , and V was escalated from 50 mg twice daily (BID) to a maximum of 200 mg BID on days 1–5 every week over 4 dose levels. In the q3wk trial, C was given on day 3 every 21 days at an AUC of 6, P was given on day 3 every 21 days with the dose escalated from 150 mg/m 2 to a dose of 200 mg/m 2 , and V was given on days 1–7 every 21 days and escalated from 10 mg BID to a dose of 120 mg BID over 9 dose levels. Toxicity was assessed by CTCAE v. 4 and response was determined using RECIST criteria. Results: The q1wk trial enrolled a total of 18 pts, 12 of whom had BC, and 10 had TNBC. One TNBC pt was BRCA-1+ and the remainder were sporadic. The trial will be completed with the enrollment of one additional patient on dose level 4. Ten breast cancer pts are evaluable for response. DLT9s included thrombocytopenia on dose levels 3 (V at 150 mg BID) and 4 (V at 200mg BID), and both occurred in TNBC pts. The range of cycles administered to TNBC pts was 1–11. The q3wk trial enrolled a total of 75 pts, 14 had BC (12 evaluable for response), and 9 had TNBC. One of these pts had a BRCA mutation; 2 pts had a variant of undetermined significance. Three DLT9s were observed on this schedule: febrile neutropenia (C at AUC 6, P at 200 mg/m 2 , V at 40 mg BID, 100 mg BID, and 120 mg BID) and grade 3 hyponatremia. No DLT9s occurred in TNBC pts. The established RP2D for the q3wk schedule is C (AUC6), P (200mg/m2) and V (100mg bid) and additional pts are being accrued to an expansion cohort. The range of cycles administered to TNBC pts was 1–14. The clinical activity in TNBC is summarized in Table 1. Responses occurred in pts who had been previously treated both in the adjuvant and metastatic settings, as well as in those who received prior taxanes. Conclusion: There is evidence of promising clinical activity and acceptable tolerability with carboplatin, paclitaxel, and veliparib on both dosing schedules. An additional 12 pts with TNBC will be accrued to the q1wk trial with pre- and post-treatment biopsies to further evaluate underlying mechanisms of sensitivity and response with regards to DNA repair pathways. Based on our phase I experience, further randomized trials are warranted in breast cancer, particularly TNBC. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr PD09-06.