ALBERT

Description: The ICES Workshop on ICES reference points (WKREF2) was tasked review the WKREF1 report and based on the outcome develop updated guidelines for the ICES reference points system and recommendations for ACOM consideration. The WKREF1 report has suggested 5 key recom- mendations to simplify and harmonise the ICES reference points framework representing a ma- jor change to the current guidelines. At WKREF2, we detailed discussions and four key concerns were raised about the proposed approach. The first related to the simplification of rules to define Blim. Around two thirds of category 1 stocks would end up as WKREF1 “Blim Type 2” where Blim would be set as a fraction of B0. The Allee effect or “depensation” maybe more important than previously thought and should be furthered explored for ICES stocks since it has important consequences for Blim. A number of challenges and issues around defining Blim using the current guidelines were documented. Some suggestions on improvement criteria were discussed including using classifiers to define spas- modic stocks and using change point algorithms to address non-stationary productivity regimes. However, further work is need to make these approaches operational and there was no consen- sus that the WKREF1 Blim types should replace the current guidelines. WKREF1 recommended that the FMSY proxy should be based on a biological proxies and should be less than the deterministic FMSY. It was pointed out that the stochastic FMSY estimated in EqSim for example, is lower than the deterministic FMSY and that the current guidelines ensure that the FMSY should not pose a more than 5% risk to Blim. A large amount of work described in WD 1 was carried out to develop an MSE framework to consistency and robustness test a candidate refer- ence point system for North East Atlantic stocks. However, WKREF2 recommended that further work needs to be carried out to condition and test the simulation framework before the conclu- sions could be adopted by ICES and incorporated into the guidelines. A number of considerations for defining MSY related reference points were discussed including using model validation and prediction skill to ensure that ICES provide robust and credible ad- vice. There is evidence that density dependence (DD) is important in the majority of ICES stocks (68% in recruitment and 54% in growth). The correct prediction of the shape and strength of density-dependence in productivity is key to predicting future stock development and providing the best possible long-term fisheries management advice. A suggested approach to use surplus production models (SPMs) to account for DD in FMSY was suggested and discussed but there was no consensus on whether that approach was appropriate. There was consensus that the FECO approach as a means of adapting target fishing mortality to medium-term changes in productiv- ity should be included in the guidelines subject to a benchmark and ACOM approval. While WKREF1 and 2 focused mainly on Category 1 stocks ToR c) called for a “simplified and harmonised set of guidelines for estimating MSY and precautionary reference points applicable in the advice framework across various ICES stock categories.” Ideally the ICES assessment cat- egories should provide equivalent risk across all stocks. This issue was discussed but no recom- mendations emerged. There was no consensus a revised reference point framework was proposed at WKREF2. How- ever, it was agreed that it should be presented here for further discussion at ACOM and other fora. The key feature of the suggested approach is that the stock status evaluation is treated in- dependent of the Advice Rule (AR). The main feature of the system is that the biomass trigger is not linked to a stock status evaluation, it is linked to the expected biomass when fishing at the target fishing mortality, in contrast to the current ICES approach. It also entailed that FMSY would also become an upper limit of fishing mortality and that the advised fishing mortality would be set at or lower than that level. WKREF2 did not discuss what to do in situations where SSB〈 Blim or alternative forms of HCR for the advice rule. Building community understanding and con- sensus around simplified and harmonised guidelines has yet to be achieved. A further workshop WKREF3 will be required to achieve that aim. The report includes 6 recommendations for ACOM consideration.

Description: ICES

Description: The main objective of the workshop was to review the recommendations of WKREF1 and con- sider how these might feed into a new reference points framework and guidelines for ICES. There were a number of presentations on the wider issues of best practice for reference points, the Allee effect, density dependence and the WKIRISH approach. The starting point was to try and develop a set of simplified and harmonised guidelines based on the WKREF1 report rather than evolving the current guidelines to include the WKREF1 conclusions. A key aspect of the meeting was to allow for discussions in order to build a shared understanding of the strengths and weakness of the current framework and of the new framework emerging from WKREF1.

Description: Published

Description: Non Refereed

Description: Background: While immunotherapy withCD19 specific CAR T cells for relapsed/refractory (R/R) B-ALL achieves MRD negative remission in nearly all patients, relapse occurs in approximately half of patients and is frequently associated with early loss of CAR T cell persistence. Low CD19 antigen burden in the bone marrow prior to lymphodepletion and rapid contraction of CAR T cells in the blood after engraftment are predictive of early loss of CAR T cell persistence. We hypothesize that episodic antigen exposure using CD19t T cell antigen presenting cells (T-APCs) can trigger CD19 CAR T cell proliferation and re-activation in vivo, resulting in more durable CAR T cell persistence and diminished risk of CD19+ relapse. Here we report our experience to date using T-APCs following CD19 CAR T cell therapy for children and young adults with R/R B-ALL on clinical trial PLAT-03 (NCT03186118). Methods: Patient-derived T-APC products were manufactured from cryopreserved CD4/CD8 selected T cells. Cells were then activated with anti-CD3/CD28 beads, transduced with a lentiviral vector to express a truncated human CD19 (CD19t), and expanded in culture for 10 days. Subjects grade 2 among the 11 subjects, and no cytokine release syndrome or neurotoxicity has been observed. An increase in detectable CD19 CAR T cells occurred in all subjects following T-APCs, and T-APCs can be transiently detected following infusion (Figure 1). Of the 10 treated subjects with low CD19 antigen burden or rapid T cell contraction, 8/10 had CAR T cell persistence beyond Day 63, as evidenced by B cell aplasia. At last follow-up, 5/10 have ongoing B cell aplasia, with a median follow up of 8.8 months (range, 2-18.5 months). The estimated 1-year leukemia free survival (LFS) is 69.2%. Conclusion: This first-in-human study of CD19t T-APCs demonstrates the ability to successfully manufacture T-APCs from stored apheresis products collected for CAR T cell production. In 11 subjects receiving at least one T-APC dose to date, there has been one T-APC infusion reaction and no other significant associated toxicity. Early evidence of efficacy demonstrated by secondary expansion of CAR T cells suggests the potential of CD19t T-APCs to enhance durable CD19 CAR T cell persistence. Figure 1 Disclosures Gardner: Novartis: Honoraria. Jensen:Bluebird Bio: Research Funding; Juno Therapeutics, a Celgene Company: Research Funding.

Description: Background: The youngest patients referred for CAR T cell therapy are those with relapsed or refractory (R/R) KMT2A-rearranged infant B-ALL. Infants with relapsed ALL following Interfant-99 therapy have a dismal reported 3-yr OS of 20.9%, indicating the need for novel therapies. Smaller patient size, heavily pre-treated disease and high leukemia burden are often characteristics of this subgroup of patients that pose unique challenges to apheresis and manufacture of a T cell product. Additionally, reports of KMT2A-rearranged leukemia undergoing lineage switch following CD19-targeting pressure raises concern for an increased risk of myeloid leukemia relapses after B-lineage targeted CAR T cell therapy in this population. Here we report our experience using CAR T cell immunotherapy for patients with R/R infant ALL enrolled on clinical trials PLAT-02 (NCT02028455) and PLAT-05 (NCT03330691). Methods: PLAT-02 is a phase 1/2 trial of CD19-specific (FMC63scFv:IgG4hinge:CD28tm:4-1BB:ζ) CAR T cells. PLAT-05 is a phase 1 trial of CD19xCD22 dual specific CAR T cells, transduced with two separate lentiviral vectors to direct the co-expression of the CD19-specific CAR above and a CD22-specific CAR (m971scFv:IgG4hinge-CH2(L235D)-CH3-CD28tm:4-1BB:ζ). Eligible subjects on both studies have R/R B-ALL, an absolute lymphocyte count ≥100 cells/µL, and were at least 1 year of age. In addition, subjects on PLAT-02 were ≥ 10kg, and ≥ 8kg on PLAT-05. For cell manufacture, apheresis products were immuno-magnetically selected for CD4 and CD8 cells. Selected T cells were activated with anti-CD3/CD28 beads, transduced, and grown in culture with homeostatic cytokines to numbers suitable for clinical use. Infant ALL subjects received a range of 5x105 to 10x106 CAR+ T cells/kg following lymphodepleting chemotherapy. Disease response assessments were required at Day 21 and Day 63 following CAR T cell infusion. Adverse events were graded according to CTCAEv4, except CRS which was graded according to 2014 Lee criteria. Results: Eighteen subjects with R/R infant ALL have enrolled on PLAT-02 (n=14) or PLAT-05 (n=4), with a median age of 22.5 months at enrollment (range: 14.5 - 40.1 months). Of these, 2 (11.1%) had primary refractory disease, 8 (44.4%) were in 1st relapse, 7 (38.9%) were in 2nd relapse and 1 (5.6%) was in 3rd or greater relapse. Ten subjects (55.6%) had an M2 marrow or greater at enrollment prior to apheresis, and 9/18 had a history of hematopoietic cell transplant (HCT). The mean ALC was 1309 cells/µL (range 253-6944). Successful CAR T cell products were manufactured in 17/18 subjects, including in 9/9 subjects with no prior history of HCT. Of these, 16/17 subjects with available products were infused, with a median follow up of 26.9 months. One subject died of disease complications prior to CAR T cell infusion. Of the 16 treated subjects, 1 is pending disease and toxicity assessments. The maximum grade of CRS was 3 and occurred in two of 15 evaluable subjects (13%) and neurotoxicity was limited to a maximum grade of 2. Fourteen of 15 (93.3%) achieved an MRD negative complete remission (MRD-CR) by Day 21. Of the 14 subjects with an MRD-CR, 6 went on to HCT with 1 subsequent CD19 negative relapse. Of the 8 subjects who did not proceed to HCT, 1 developed lineage switch at one month following CAR T cells, and 1 died of infectious complications with aplasia. A "wait and watch" approach was taken for the remaining 6 subjects, and 2 developed CD19+ relapse. The incidence of lineage switch among the infant ALL group was 1/15 (6.7%). The estimated 1-year LFS was 66.7% and 1-year OS was 71.4%. Conclusion: This is the largest reported cohort to date of R/R infant B-ALL subjects treated with CAR T cell therapy. We report successful manufacture and administration of a CAR T cell product in the significant majority of infant subjects. Toxicity and MRD-CR rates are comparable to that of non-infant ALL subjects. In our experience, subjects with R/R infant ALL are not at increased risk for lineage switch relapse compared with the entire study populations following B-antigen targeting CAR T cell immunotherapy. Numbers in this report are too small to make definitive conclusions about the value of consolidative HCT. However, the LFS of this cohort is remarkably higher when compared with historical controls. Future work is focused on overcoming feasibility issues for the smallest of subjects, to enable a larger number of these cases to access CAR T cell therapy. Disclosures Pulsipher: Amgen: Other: Lecture; Bellicum: Consultancy; Miltenyi: Research Funding; Medac: Honoraria; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Jazz: Other: Education for employees; Adaptive: Membership on an entity's Board of Directors or advisory committees, Research Funding; CSL Behring: Membership on an entity's Board of Directors or advisory committees. Wayne:AbbVie: Consultancy; Spectrum Pharmaceuticals: Consultancy, Research Funding; Servier: Consultancy; Kite, a Gilead Company: Consultancy, Research Funding. Jensen:Bluebird Bio: Research Funding; Juno Therapeutics, a Celgene Company: Research Funding. Gardner:Novartis: Honoraria.

Description: Little is known about the disease-specific factors that predict responsiveness to CAR-T cell therapy, other the direct presence of the CAR-T target. Clinical outcomes at our center have demonstrated that durable responses to CD19-directed CAR-T therapy in pediatric pre-B-ALL (acute lymphoblastic leukemia) are associated with persistence of CAR-T cells in the peripheral blood, antigenic load (percent CD19-positive cells in marrow prior to CAR-T infusion), and apheresis product T-cell quality (Finney O, et al., 2019). However, in a small number of cases where both antigenic load and T-cell quality predicted a good response, the treatment failed rapidly. This led us to undertake a detailed investigation of the leukemia itself in order to discover potential disease-associated factors that correlate with resistance to CAR-T therapy. We employed advanced exomic, and single-cell genomic and epigenomic analysis techniques to define signatures present in four CD19-CAR-T resistant bone marrow biopsy specimens, in comparison to five specimens from CD19-CAR-T responsive disease, from patients enrolled in a phase I clinical trial at Seattle Children's Hospital (PLAT-02, NCT02028455). Current cytogenic approaches to identify high risks markers (Ph+, Ph-like, MLL) were not informative as to CAR-T susceptibility, as high risk leukemias were CAR-T responsive; while a CAR-T resistant leukemia contained a marker (ETV6-RUNX1 fusion) previously associated with a good prognosis. Thus, we performed bulk whole-exome sequencing and RNAseq, single cell (sc) RNAseq, sc B-cell receptor (BCR)-seq, methylation array, H3K27ac ChIPseq, and ATACseq on these marrow samples. Initial genomic analysis revealed a total of 5 previously described hotspot mutations in ABL1, IKZF1, EP300, and 2 in KRAS. RNAseq analyses identified actionable fusions for ABL1, ETV6, ETV5, and KMT2A. Interestingly, a therapy-sensitive leukemia harbored a KMT2A-AFF1 fusion that was shown to predispose patients to leukemic plasticity and lineage switching when treated with blinatumomab. Importantly, we identified CREBBP-fusions in leukemias that failed to achieve CD19-CAR-T cell induced B cell aplasia. CREBBP perturbations have previously been associated with relapsed and refractory ALL, but not with resistance to CAR-T therapy. Single cell RNAseq and scBCRseq data are being analyzed for the existence of mixed lineage and gene expression-based heterogeneity that may predict clonal selection under CAR-T pressure. RNASeq analysis identified upregulation of JUN and JUND transcripts in CAR-T resistant disease, a finding which is complemented by the hypermethylation of JUND in CAR-T sensitive disease. Similarly, ATACseq and methylation data is being analyzed for lineage specification in CAR-T resistant leukemia. In comparing dysfunctional to functional CAR-T responders by ATACseq, 〉 10,000 unique open chromatin regions were identified in dysfunctional responders, as opposed to