ALBERT

Description: Background: The Stroke Prevention Trial in Sickle Cell Anemia (STOP) and Optimizing Primary Stroke Prevention in Sickle Cell Anemia (STOP 2) established routine transcranial Doppler ultrasound (TCD) screening with indefinite chronic red cell transfusions (CRCT) for children with abnormal TCD as standard of care. To identify children at high-risk of stroke, annual TCD screening is recommended from ages 2 to 16 years, with more frequent monitoring if the result is not normal. A reduction in stroke incidence in children with SCD has been reported in several clinical series and analyses utilizing large hospital databases when comparing rates before and after the publication of the STOP study in 1998. We sought to determine the rate of first ischemic stroke in a multicenter cohort of children who had previously participated in the STOP and/or STOP 2 trials and to determine whether these strokes were screening or treatment failures. Subjects and Methods: Between 1995 and 2005, STOP and STOP 2 (STOP/2) were conducted at 26 sites in the US and Canada. These studies included 3,835 children, ages 2 to 16 y with SCD type SS or S-beta-0-thalassemia. Participation in STOP/2 ranged from a single screening TCD to randomization. STOP 2 also had an observational arm for children on CRCT for abnormal TCD whose TCD had not reverted to normal. The Post-STOP study was designed to follow-up the outcomes of children who participated in one or both trials. 19 of the 26 original study sites participated in Post-STOP, contributing a total of 3,539 (92%) of the STOP/2 subjects. After exit from STOP/2, these children received TCD screening and treatment according to local practices. Data abstractors visited each clinical site and obtained retrospective data from STOP/2 study exit to 2012-2014 (depending on site) including follow-up TCD and brain imaging results, clinical information, and laboratory results. Two vascular neurologists, blinded to STOP/2 status and prior TCD and neuroimaging results, reviewed source records to confirm all ischemic strokes, defined as a symptomatic cerebral infarction; discordant opinions were resolved through discussion. For the first Post-STOP ischemic stroke, prior TCD result and treatment history subsequently were analyzed. Results: Of the 3,539 subjects, follow-up data were available for 2,850 (81%). Twelve children who had a stroke during STOP or STOP2 were excluded from these analyses resulting in data on 2,838 subjects. The mean age at the start of Post-STOP was 10.5 y and mean duration of follow-up after exiting STOP/2 was 9.1 y. A total of 69 first ischemic strokes occurred in the Post-STOP observation period (incidence 0.27 per 100 pt years). The mean age at time of stroke was 14.4±6.2 (median 13.8, range 3.5-28.9) y. Twenty-five of the 69 patients (36%) had documented abnormal TCD (STOP/2 or Post-STOP) prior to the stroke; 15 (60%) were receiving CRCT and 9 (36%) were not (treatment data not available for 1 subject). Among the 44 subjects without documented abnormal TCD, 29 (66%) had not had TCD re-screen in the Post-STOP period prior to the event; 7 of these 29 (24%) were 16 y or older at the start of Post-STOP, which is beyond the recommended screening age. Four of the 44 (9%) patients had inadequate TCD in Post-STOP (1 to 10.7 y prior to event). Six (14%) had normal TCD more than a year before the event (1.2 - 4 y); all but one of these children were younger than 16 y at the time of that TCD. Only 5 (11%) had a documented normal TCD less than 1 year prior to the event. Conclusions: In the Post-STOP era, the rate of first ischemic stroke was substantially lower than that reported in the Cooperative Study of Sickle Cell Disease, prior to implementation of TCD screening. Many (39%) of the Post-STOP ischemic strokes were associated with a failure to re-screen according to current guidelines, while only 11% occurred in children who had had recent low-risk TCD. Among those known to be at high risk prior to stroke, treatment refusal or inadequate treatment may have contributed. While TCD screening and treatment are effective at reducing ischemic stroke in clinical practice, significant gaps in screening and treatment, even at sites experienced in the STOP protocol, remain to be addressed. Closing these gaps should provide yet further reduction of ischemic stroke in SCD. Disclosures No relevant conflicts of interest to declare.

Description: Background: The Stroke Prevention Trial in Sickle Cell Anemia (STOP) and Optimizing Primary Stroke Prevention in Sickle Cell Anemia (STOP 2) study established routine transcranial Doppler ultrasound (TCD) screening with indefinite transfusions for children with abnormal TCD as standard of care. Children with normal TCD studies have the lowest risk of stroke of ~0.5-1% per year (y). Annual TCD screening is usually recommended for these children to detect possible subsequent conversion to high risk. We sought to determine the frequency of TCD screening utilized in “real world” clinical practice and the TCD outcomes for children with prior normal TCD. Subjects and Methods: During STOP and STOP2 (STOP/2), 3,837 children, ages 2 to 16 y with sickle cell disease type SS or S-Beta-0-thalassemia underwent screening TCD. The Post-STOP study was designed to follow-up the outcomes of children who were screened for or participated in one or both of these randomized trials. 19 of the 26 original study sites participated in Post-STOP, contributing a total of 3,541 (92%) of the STOP/2 subjects. After exit from STOP/2, these children received TCD screening and treatment according to local practices. Data abstractors visited each clinical site and obtained retrospective data from STOP/2 study exit to 2012-2014 (depending on site) on follow-up TCD results and clinical information using standard data collection forms. The rates of TCD re-screening and the proportion of children who converted to abnormal TCD were calculated. Factors associated with conversion to abnormal TCD were assessed. Results: Of the 3,541 subjects, follow-up data were available for 2,838 (80%). The mean age at the last TCD study obtained in STOP/2 was 9.5 y and the mean age at last follow-up in Post-STOP was 19.6 y. The mean duration of follow-up after exiting STOP/2 was 9.2 y. Subjects were classified by their worst TCD in STOP/2: the TCD was normal in 1,814 (64%), conditional in 479 (17%), abnormal in 357 (13%) and inadequate 188 (7%). Among the 1,814 children with only normal studies in STOP/2, follow-up TCD screening was obtained in the Post-STOP era on 842 (46%) at a median rate of 0.28 TCD studies/y (range, 0.05-3.04/y). Among these children, 26 (3.1%) developed an abnormal TCD at a median of 11.5 y (2.2-18.2 y) from the last STOP/2 study, while 77.5% still had normal TCD at a median of 10.7 y (0.7-18.3 y) from last STOP/2 study. The worst follow-up TCD classification for this group with prior normal TCD was conditional in 9.7% and inadequate in 9.6%. Among those that converted from prior normal to abnormal TCD, 12 had an interval conditional study (at median 2.8 y, 0.98-9.2 y) while 14 children converted from normal to abnormal at a median of 4.2 y (1.4-12.7 y) without documented interval conditional study. Children who developed abnormal TCD were younger at STOP/2 study exit (4.9 vs. 7.8 y, p

Description: Background: Primary hemorrhagic stroke is a rare complication of sickle cell disease (SCD) that usually occurs in adults. The Stroke Prevention Trial in Sickle Cell Anemia (STOP) and Optimizing Primary Stroke Prevention in Sickle Cell Anemia (STOP 2) established routine transcranial Doppler ultrasound (TCD) screening with indefinite chronic red cell transfusions (CRCT) for patients with abnormal TCD as standard of care. Despite a notable improvement in the incidence of infarctive stroke in children with SCD after the introduction of TCD screening protocols, it is unclear how this protocol will affect the rate of hemorrhagic stroke. Presumably, early TCD screening and subsequent initiation of CRCT in high risk patients will prevent the progression of cerebral vasculopathy, which should decrease the risk of hemorrhagic stroke; however this has not been proven. Using the large multicenter cohort of children who participated in STOP and/or STOP 2 trials, we sought to assess whether the rate of hemorrhagic stroke was impacted by the use of TCD screening and/or CRCT. Subjects and Methods: Between 1995 and 2005, STOP and STOP 2 (STOP/2) were conducted at 26 sites in the US and Canada. These studies included 3835 children, ages 2 to 16 y with SCD type SS or S-beta-0-thalassemia. Participation in STOP/2 required at least a single screening TCD for randomization. Patients on STOP 2 also had an observational arm for children started on CRCT who had an abnormal TCD. The Post-STOP study was designed to follow-up the outcomes of children who participated in one or both of trials. For all participants the date of their last encounter in STOP/2 was defined as the start of their Post-STOP period. 19 of the 26 original study sites participated in Post-STOP, contributing a total of 3539 (92%) of the STOP/2 subjects. After exit from STOP/2, these children received TCD screening and treatment according to local practices. Data abstractors visited each clinical site and obtained retrospective data from STOP/2 study exit to 2012-2014 including follow-up TCD and brain imaging results, clinical information, and laboratory results. Two separate neurologists, blinded to STOP/2 status and prior TCD and neuroimaging results adjudicated all suspected strokes. Results: Follow-up data were available for 2850 of the 3539 subjects (81%). Twelve children who had a stroke during the STOP study period were further excluded from this analysis resulting 2838 subjects. The mean age at the start of Post-STOP was 10.5 years and mean duration of follow-up after exiting STOP/2 until time of last medical encounter was 9.1 years. A total of 31 patients had a primary hemorrhagic stroke during the Post-STOP observation period (incidence 0.12 per 100 pt years). The mean age at time of stroke was 16.2+5.6 (median 15.3 range (4.8-30.2) years of age. Of those 31 patients, only 52% had a TCD during Post-STOP prior to the event. Seven of those children who underwent screening had documentation of an abnormal TCD prior to the event (5 during STOP era and/or 3 Post-STOP). However, only 1/7 patients (14%) were documented on CRCT at the time of the stroke (4 patients were receiving HU and 2 patients had unknown treatment). Discussion: Although less common than infarctive stroke, patients with SCD are at increased risk for hemorrhagic stroke. There is an increased risk of mortality for patients who suffer from hemorrhagic stroke (up to 26% in some reports in the 2 weeks after the event). It is unclear if TCD screening and subsequent initiation of CRCT will impact the rate of hemorrhagic stroke in the long term. In our results, a similar incidence of primary hemorrhagic stroke was noted although the patients were overall younger than previously reported (16.5+/- 5.5 years versus 20-29 years in Cooperative Study of Sickle Cell Disease). Many patients who had a hemorrhagic stroke (48%) had not undergone TCD screening during the Post-Stop period. Additionally, although a safe stopping point for CRCT has not been established in patients who have had an abnormal TCD, only 1 patient was documented on CRCT at the time of the event (14%). Thus, it is unclear at this time whether TCD screening and subsequent, lifelong continuation of CRCT could have prevented these other events. Clearly, these results demonstrate that improved implementation of STOP protocol is needed as well as further evaluation of the impact of this protocol on the incidence of hemorrhagic stroke. Disclosures No relevant conflicts of interest to declare.

Description: CD47 is an anti-phagocytic (i.e. "don't eat me") signal and macrophage checkpoint that cancer cells utilize to evade innate immunity and establish disease. 5F9 is a humanized IgG4 monoclonal antibody (mAb) that binds to human CD47 and blocks its interaction with SIRPα, its cognate inhibitory receptor.5F9 is undergoing investigation in several clinical trials and preliminary analyses have revealed encouraging therapeutic potential. We previously established that administration of 5F9 clears a subset of aged RBCs, resulting in a compensatory reticulocytosis. This occurs transiently, predominantly after the first dose, and does not worsen with subsequent doses. These findings, aligned with the observations of Oldenborg et al., which established that removal of aged RBCs, is dependent on the balance between the accumulating pro-phagocytic signals and loss of inhibitory anti-phagocytic signals. We therefore hypothesized that an initial lower 5F9 "priming dose", sufficient to trigger clearance of aged RBCs, would yield an overall younger pool of RBCs that are less vulnerable to subsequent higher 5F9 therapeutic "maintenance doses". Indeed, this priming and maintenance dosing strategy has substantially mitigated the on-target anemia and has allowed for 5F9 treatment in multiple clinical trials and indications. To further probe this observed selective RBC clearance, we employed a receptor occupancy assay to quantitate the CD47 expression on the cell surface of RBCs, leukocytes (WBCs), and acute myeloid leukemia (AML) blasts. We discovered that the priming dose of 5F9 not only triggered clearance of a subset of RBCs, but also resulted in a near complete loss of CD47 - a phenomenon we term CD47 pruning. This effect was RBC-specific, as WBCs and AML bone marrow (BM) blasts did not exhibit this same CD47 pruning (Fig 1). To explore the functional consequence of these unexpected clinical findings, we investigated whether we could recapitulate them in a preclinical mouse model. Similar to the clinical setting, anti-mouse CD47 blocking Ab treatments exhibited a similar pruning effect and transient anemia. Using this model, we asked whether, in the context of anti-CD47 treatment, these pruned RBCs were protected compared to unpruned RBCs. We transfused fluorescently labeled RBCs from CD47 Ab-untreated and CD47-treated mice into animals receiving continuous anti-CD47 treatment. We observed that CD47-pruned RBCs exhibited a significantly longer half-life compared to unpruned RBCs, suggesting that CD47 pruning is protective for RBCs. To distinguish whether this protection is cell-intrinsic or cell-extrinsic, we transfused fluorescently labeled RBCs into CD47 Ab-untreated and -treated mice and observed that CD47-pruned RBCs are rapidly cleared in untreated recipients, suggesting that this treatment-induced protection of RBCs is cell extrinsic and a host-based alteration. Through depletion of distinct immune subsets by chemical depletion, antibody depletion, splenectomy, and partial hepatectomies, we demonstrated that host immune effector cells (e.g. red-pulp macrophages, neutrophils, T cells etc.) were not necessary for this pruning phenomenon. Critically, we also found that this CD47 pruning and resulting tolerance was Fc-independent. In order to understand whether these findings were generalizable to other anti-human CD47 blocking agents, we conducted similar studies in double humanized huCD47 and huSIRPa micewith additional agents and observed this same CD47 pruning and tolerance phenomenon. Thereby suggesting this represents a class-effect of this emerging potential therapy class. Notably, these clinical and pre-clinical findings have been RBC-specific and have not precluded anti-tumor efficacy. The loss of CD47 on RBCs after the priming dose also suggests that the potential risk of CD47 Ab-mediated RBC agglutination following subsequent maintenance dosing is substantially reduced. Unlike prior RBC antigen modulation reports, to our knowledge, these findings represent a novel RBC antigen depletion phenomenon that is independent of the known RBC regulatory compartments, including the spleen, liver, major immune effectors cells, complement, and is critically Fc-independent. These findings provide fundamental insight into the mechanism underlying how anti-CD47 Abs are tolerated without impairing therapeutic efficacy. Disclosures Chen: Forty Seven Inc: Consultancy, Equity Ownership. McKenna:Forty Seven Inc.: Equity Ownership. Choi:Forty Seven Inc: Employment, Equity Ownership. Duan:Forty Seven Inc: Employment, Equity Ownership. Sompalli:Forty Seven Inc: Employment, Equity Ownership. Schrier:Forty Seven Inc.: Consultancy. Weissman:Forty Seven, Inc: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties. Elrod:Forty Seven Inc.: Employment, Equity Ownership. Chao:Forty Seven Inc: Employment, Equity Ownership, Patents & Royalties. Takimoto:Forty Seven Inc: Employment, Equity Ownership, Patents & Royalties. Liu:Forty Seven Inc: Employment, Equity Ownership, Patents & Royalties. Volkmer:Forty Seven Inc: Employment, Equity Ownership, Patents & Royalties.

Description: A limited number of preplant (PP) herbicides are available for spring seeded cereals in Ontario. Six field trials were conducted at the Huron Research Station, Exeter, Ontario, over a two-year period (Exeter, 2010 and 2011) to evaluate glyphosate, prosulfuron, and glyphosate plus prosulfuron applied PP for weed management in spring seeded no-till barley, oats, and wheat. There was no injury in barley, oats, and wheat with glyphosate, prosulfuron, and glyphosate plus prosulfuron applied preplant at the rates evaluated at 1, 2, and 4 weeks after crop emergence. Prosulfuron provided 49–99% control of AMBEL, 28% or less control of CONAR, 31–94% control of POLCO, 49–98% control of SINAR, and 46–79% control of SONAR. Prosulfuron in combination with glyphosate provided 73–98% control of AMBEL, less than 43% control of CONAR, 39–94% control of POLCO, 63–98% control of SINAR, and 60–85% control of SONAR. Prosulfuron reduced density of AMBEL 76% and SINAR 93% but had no significant effect on density of CONAR, POLCO, or SONAR. Prosulfuron in combination with glyphosate reduced biomass of AMBEL as much as 96% and SINAR 98% but had no significant effect on biomass of CONAR, POLCO, or SONAR. Yield of barley, oats, and wheat was not affected with glyphosate, prosulfuron, and glyphosate plus prosulfuron at the rates evaluated.

Description: Six field experiments were conducted during 2015 to 2017 in Ontario, Canada, to determine the efficacy of pethoxamid applied alone, and in combination with broadleaf herbicides, for the control of annual grass and broadleaved weeds in white navy bean. Visible injury was generally minimal (0 to 8%) with herbicide treatments evaluated. Weed control was variable depending on the weed species evaluated. Pethoxamid,S-metolachlor, halosulfuron, imazethapyr, sulfentrazone, pethoxamid + halosulfuron, pethoxamid + imazethapyr, and pethoxamid + sulfentrazone controlled redroot pigweed 82 to 98%; common ragweed 19 to 93%; common lambsquarters 49 to 84%; and green foxtail 47 to 92% in white bean. Weed biomass and weed density reductions were similar to visible control ratings for herbicides evaluated. Weed interference delayed white bean maturity and reduced yield by 50% in this study. Weed interference in plots sprayed with pethoxamid,S-metolachlor, and sulfentrazone reduced white bean yield 36%. White bean yield was similar to the weed-free with other herbicides evaluated. This study concludes that there is potential for the tank-mix of pethoxamid with halosulfuron, imazethapyr, or sulfentrazone for weed control in white bean production.