Costs per patient achieving remission with venetoclax-based combinations in newly diagnosed patients with acute myeloid leukemia ineligible for intensive induction chemotherapy.

BACKGROUND: Venetoclax, in combination with azacitidine, decitabine, or low-dose cytarabine (LDAC), received confirmatory approval in 2020 by the US Food and Drug Administration for the treatment of newly diagnosed acute myeloid leukemia (AML) in patients aged 75 years or older or who are ineligible for intensive induction chemotherapy. The economic value associated with response to venetoclax combinations compared with other treatments for this patient population has not been comprehensively evaluated. OBJECTIVE: To assess the cost per patient achieving remission with venetoclax combination therapies, compared with other therapies for newly diagnosed patients with AML who are ineligible for intensive induction chemotherapy, from a US third-party payer perspective. METHODS: The analysis used treatment effect estimates (ie, complete remission [CR] + CR with incomplete blood count recovery [CRi]) from a network meta-analysis and annual cost estimates from a prior budget impact model. The model considered the total cost of care including the costs of drug and administration, adverse events, hospitalization, disease monitoring, blood transfusions, and subsequent AML management when patients discontinued active treatment. Costs per patient achieving CR + CRi associated with venetoclax + azacitidine, venetoclax + LDAC, azacitidine, decitabine, LDAC, and best supportive care (ie, treatment given with the intent to maximize quality of life without specific antileukemic intent, such as blood transfusion products and antibiotics) were calculated as the annual total cost of care per patient divided by the CR + CRi rate. All costs were adjusted to 2020 US dollars. RESULTS: Venetoclax combination therapies were estimated to have substantially lower costs per patient achieving CR + CRi (venetoclax + azacitidine: $473,960; venetoclax + LDAC: $428,071) than alternative treatments. Azacitidine was estimated to have the the highest cost per patient achieving CR + CRi ($1,197,438), followed by best supportive care ($869,849), LDAC ($689,101), and decitabine ($594,074). A pair-wise matrix of the difference between therapies estimated that both venetoclax + azacitidine and venetoclax + LDAC were associated with significantly lower costs per patient achieving CR + CRi than azacitidine (by $723,477 and $769,367, respectively) and LDAC (by $215,141 and $261,030; all P < 0.05). CONCLUSIONS: From a US third-party payer perspective, venetoclax in combination with azacitidine or LDAC was estimated to be associated with a significantly lower cost per patient achieving CR + CRi than azacitidine or LDAC among newly diagnosed patients with AML ineligible for intensive chemotherapy. DISCLOSURES: This research was supported by AbbVie Inc. and Genentech. The sponsors helped design the study, interpret the data, and draft the manuscript. Drs Bui and Kapustyan are employees of and have equity ownership in AbbVie; Dr Choi was an employee of AbbVie during the study's conduct and has equity ownership. Ms Ma and Dr Montez are employees of and have equity ownership in Genentech. Drs Song and Chai, Ms Yin, and Dr Betts are employees of Analysis Group, Inc., which has received funding from AbbVie and Genentech for the conduct of this research. Dr LeBlanc reports personal fees for consulting or advisory boards from AbbVie, Agios/Servier, AstraZeneca, Amgen, Astellas, BlueNote, CareVive, BMS/Celgene, Daiichi-Sankyo, Flatiron, Genentech, GSK, Pfizer, and Seattle Genetics; royalties from UpToDate; speakers bureau fees from Agios/Servier, AbbVie, and BMS/Celgene; and grants and/or research contracts from the American Cancer Society, AstraZeneca, BMS, Jazz Pharmaceuticals, and Seattle Genetics.

Sacubitril/Valsartan Initiation Among Veterans Who Are Renin-Angiotensin-Aldosterone System Inhibitor Naïve With Heart Failure and Reduced Ejection Fraction.

Background Sacubitril/valsartan, a first-in-class angiotensin receptor neprilysin inhibitor, received US Food and Drug Administration approval in 2015 for heart failure with reduced ejection fraction (HFrEF). Our objective was to describe the sacubitril/valsartan initiation rate, associated characteristics, and 6-month follow-up dosing among veterans with HFrEF who are renin-angiotensin-aldosterone system inhibitor (RAASi) naïve. Methods and Results Retrospective cohort study of veterans with HFrEF who are RAASi naïve defined as left ventricular ejection fraction (LVEF) ≤40%; ≥1 in/outpatient heart failure visit, first RAASi (sacubitril/valsartan, angiotensin-converting enzyme inhibitor [ACEI]), or angiotensin-II receptor blocker [ARB]) fill from July 2015 to June 2019. Characteristics associated with sacubitril/valsartan initiation were identified using Poisson regression models. From July 2015 to June 2019, we identified 3458 sacubitril/valsartan and 29 367 ACEI or ARB initiators among veterans with HFrEF who are RAASi naïve. Sacubitril/valsartan initiation increased from 0% to 26.5%. Sacubitril/valsartan (versus ACEI or ARB) initiators were less likely to have histories of stroke, myocardial infarction, or hypertension and more likely to be older and have diabetes mellitus and lower LVEF. At 6-month follow-up, the prevalence of ≥50% target daily dose for sacubitril/valsartan, ACEI, and ARB initiators was 23.5%, 43.2%, and 47.1%, respectively. Conclusions Sacubitril/valsartan initiation for HFrEF in the Veterans Administration increased in the 4 years immediately following Food and Drug Administration approval. Sacubitril/valsartan (versus ACEI or ARB) initiators had fewer baseline cardiovascular comorbidities and the lowest proportion on ≥50% target daily dose at 6-month follow-up. Identifying the reasons for lower follow-up dosing of sacubitril/valsartan could support guideline recommendations and quality improvement strategies for patients with HFrEF.

Respiratory events associated with concomitant opioid and sedative use among Medicare beneficiaries with chronic obstructive pulmonary disease.

BACKGROUND: Opioids and sedatives are commonly prescribed in chronic obstructive pulmonary disease (COPD) patients for symptoms of dyspnoea, pain, insomnia, depression and anxiety. Older adults are advised to avoid these medications due to increased adverse events, including respiratory events. This study examines respiratory event risks associated with concomitant opioid and sedative use compared with opioid use alone in older adults with COPD. METHODS: A 5% nationally representative sample of Medicare beneficiaries with COPD and opioid use between 2009 and 2013 was used for this retrospective cohort study. Current and past concomitant use were identified using drug dispensed within 7 days from the censored date: at respiratory event, at death, or at 12 months post index. Concomitant opioid and sedative use were categorised into no overlap (opioid only), 1 to 10, 11 to 30, 31 to 60 and >60 days of total overlap. The primary outcome was hospitalisation or emergency department (ED) visits for respiratory events (COPD exacerbations or respiratory depression). Propensity score matching was implemented and semi-competing risk models were used to address competing risk by death. RESULTS: Among 48 120 eligible beneficiaries, 1810 (16.7%) concomitant users were matched with 9050 (83.3%) opioid only users. Current concomitant use of 1 to 10, 11 to 30 and 31 to 60 days was associated with increased respiratory events (HRs (95% CI): 2.8 (1.2 to 7.3), 9.3 (4.9 to 18.2) and 5.7 (2.5 to 12.5), respectively), compared with opioid only use. Current concomitant use of >60 days or past concomitant use of ≤60 days was not significantly associated with respiratory events. Consistent findings were found in sensitivity analyses, including in subgroup analysis of non-benzodiazepine sedatives. Additionally, current concomitant use significantly increased risk of death. CONCLUSION: Short-term and medium-term current concomitant opioid and sedative use significantly increased risk of respiratory events and death in older COPD Medicare beneficiaries. Long-term past concomitant users, however, demonstrated lower risks of these outcomes, possibly reflecting a healthy user effect or developed tolerance to the effects of these agents.

Characteristics and Healthcare Utilization Among Veterans Treated for Heart Failure With Reduced Ejection Fraction Who Switched to Sacubitril/Valsartan.

BACKGROUND: US guidelines recommend that patients with heart failure with reduced ejection fraction (HFrEF), who tolerate an ACEI (angiotensin-converting enzyme inhibitor) or ARB (angiotensin II receptor blocker), be switched to sacubitril/valsartan to reduce morbidity and mortality. We compared characteristics and healthcare utilization between Veterans with HFrEF who were switched to sacubitril/valsartan versus maintained on an ACEI or ARB. METHODS: retrospective cohort study of treated HFrEF (July 2015-June 2017) using Veterans Affairs data. The index date was the first fill for sacubitril/valsartan and if none, for an ACEI or ARB. Treated HFrEF was defined by (1) left ventricular ejection fraction ≤40%, (2) ≥1 in/outpatient HF encounter, and (3) ≥1 ACEI or ARB fill, all within 1-year preindex. Poisson regression models were used to compare baseline characteristics and 1:1 propensity score-matched adjusted 4-month follow-up healthcare utilization between sacubitril/valsartan switchers and ACEI or ARB maintainers. RESULTS: Switchers (1612; 4.2%) were less likely than maintainers (37 065; 95.8%) to have a history of myocardial infarction or hypertension, and more likely to be black, have a lower left ventricular ejection fraction, and higher preindex healthcare utilization. Switchers were less likely to experience follow-up all-cause hospitalizations (11.2% versus 14.0%; risk ratio 0.80 [95% CI, 0.65-0.98], P value 0.035). CONCLUSIONS: Few Veterans with treated HFrEF were switched to sacubitril/valsartan within the first 2 years of Food and Drug Administration approval. Sacubitril/valsartan use was associated with a lower risk for all-cause hospitalizations at 4 months follow-up. Reasons for lack of guideline-recommended sacubitril/valsartan initiation warrant investigation and may reveal opportunities for HFrEF care optimization.

The DAGMAR Score: D-dimer assay-guided moderation of adjusted risk. Improving specificity of the D-dimer for pulmonary embolism.

We generated a novel scoring system to improve the test characteristics of D-dimer in patients with suspected PE (pulmonary emboli). Electronic Medical Record data were retrospectively reviewed on Emergency Department (ED) patients 18 years or older for whom a D-dimer and imaging were ordered between June 4, 2012 and March 30, 2016. Symptoms (dyspnea, unilateral leg swelling, hemoptysis), age, vital signs, medical history (cancer, recent surgery, medications, history of deep vein thrombosis or PE, COPD, smoking), laboratory values (quantitative D-dimer, platelets, and mean platelet volume (MPV)), and imaging results (CT, VQ) were collected. Points were designated to factors that were significant in two multiple regression analyses, for PE or positive D-dimer. Points predictive of PE were designated positive values and points predictive of positive D-dimer, irrespective of presence of PE, were designated negative values. The DAGMAR (D-dimer Assay-Guided Moderation of Adjusted Risk) score was developed using age and platelet adjustment and points for factors associated with PE and elevated D-dimer. Of 8486 visits reviewed, 3523 were unique visits with imaging, yielding 2253 (26.5%) positive D-dimers. 3501 CT scans and 156 VQ scans were completed, detecting 198 PE. In our cohort, a DAGMAR Score < 2 equated to overall PE risk < 1.2%. Specificity improved (38% to 59%) without compromising sensitivity (94% to 96%). Use of the DAGMAR Score would have reduced CT scans from 2253 to 1556 and lead to fewer false negative results. By considering factors that affect D-dimer and also PE, we improved specificity without compromising sensitivity.

Placement of selected new FDA-approved drugs in Medicare Part D formularies, 2009-2013.

OBJECTIVES: To assess formulary decisions by Part D plans for selected newly approved drugs. STUDY DESIGN: Retrospective cohort study. METHODS: Formulary placement and restrictions were identified for 33 drugs in 8 therapeutic classes (antihyperglycemics, anticoagulants, antiplatelets, disease-modifying agents for multiple sclerosis [MS] and rheumatoid arthritis [RA], chronic obstructive pulmonary disease [COPD] drugs, antiepileptics, and antipsychotics) in 863 Part D plans with continuous CMS contracts between 2009 and 2013. Multivariable models estimated the impact of drug characteristics and Part D plan characteristics on probability of drug adoption and, for adopters, evaluated factors associated with months to adoption and requirements for prior authorization (PA) or step therapy (ST). RESULTS: First Part D formulary placements varied from 2 to 14 months post FDA approval. On average, 56.7% of plans placed each drug within 6 months and 64.1% placed within 1 year of the National Drug Code assignment date. The most rapid adoption was for antipsychotics and antiepileptics. The slowest was for COPD drugs. More than 90% of disease-modifying agents for MS and RA were subject to PA. ST was uncommon except for antihyperglycemic agents. In adjusted analyses, enhanced benefit plans had a 4% higher probability of formulary placement (P <.01), and each additional star in the CMS star rating system increased the probability of adoption by 4% (P <.01). Overall, Medicare Advantage prescription drug plans had higher placement rates due to greater reliance on enhanced plan offerings and higher star ratings. CONCLUSIONS: We found significant heterogeneity in formulary placement and restrictions for 33 new drugs in the Part D marketplace between 2009 and 2013. Further research is necessary to determine whether this pattern applies to other drug classes.

Use of the d-dimer for Detecting Pulmonary Embolism in the Emergency Department.

BACKGROUND: Assessment for pulmonary embolism (PE) in the emergency department (ED) remains complex, involving clinical decision tools, blood tests, and imaging. OBJECTIVE: Our objective was to examine the test characteristics of the high-sensitivity d-dimer for the diagnosis of PE at our institution and evaluate use of the d-dimer and factors associated with a falsely elevated d-dimer. METHODS: We retrospectively collected data on adult patients evaluated with a d-dimer and computed tomography (CT) pulmonary angiogram or ventilation perfusion scan at two EDs between June 4, 2012 and March 30, 2016. We collected symptoms (dyspnea, unilateral leg swelling, hemoptysis), vital signs, and medical and social history (cancer, recent surgery, medications, history of deep vein thrombosis or PE, chronic obstructive pulmonary disease, smoking). We calculated test characteristics, including sensitivity, specificity, and likelihood ratios for the assay using conventional threshold and with age adjustment, and performed a univariate analysis. RESULTS: We found 3523 unique visits with d-dimer and imaging, detecting 198 PE. Imaging was pursued on 1270 patients with negative d-dimers, revealing 9 false negatives, and d-dimer was sent on 596 patients for whom negative Pulmonary Embolism Rule-Out Criteria (PERC) were documented with 2% subsequent radiographic detection of PE. The d-dimer showed a sensitivity of 95.7% (95% confidence interval [CI] 91-98%), specificity of 40.0% (95% CI 38-42%), negative likelihood ratio of 0.11 (95% CI 0.06-0.21), and positive likelihood ratio of 1.59 (95% CI 1.53-1.66) for the radiographic detection of PE. With age adjustment, 347 of the 2253 CT scans that were pursued in patients older than 50 years with an elevated d-dimer could have been avoided without missing any additional PE. Many risk factors, such as age, history of PE, recent surgery, shortness of breath, tachycardia and hypoxia, elevated the d-dimer, regardless of the presence of PE. CONCLUSIONS: Many patients with negative d-dimer and PERC still received imaging. Our data support the use of age adjustment, and perhaps adjustment for other factors seen in patients evaluated for PE.

The C-terminal heme regulatory motifs of heme oxygenase-2 are redox-regulated heme binding sites.

Heme oxygenase-2 (HO2), an enzyme that catalyzes the conversion of heme to biliverdin, contains three heme regulatory motifs (HRMs) centered at Cys127, Cys265, and Cys282. Previous studies using the soluble form of human HO2 spanning residues 1-288 (HO2sol) have shown that a disulfide bond forms between Cys265 and Cys282 and that, in this oxidized state, heme binds to the catalytic site of HO2sol via His45. However, various mutational and spectroscopic studies have confirmed the involvement of cysteine in Fe(3+)-heme binding upon reduction of the disulfide bond. In an effort to understand how the HRMs are involved in binding of heme to disulfide-reduced HO2sol, in the work described here, we further investigated the properties of Fe(3+)-heme bound to HO2. Specifically, we investigated binding of Fe(3+)-heme to a truncated form of soluble HO2 (residues 213-288; HO2tail) that spans the C-terminal HRMs of HO2 but lacks the catalytic core. We found that HO2tail in the disulfide-reduced state binds Fe(3+)-heme and accounts for the spectral features observed upon binding of heme to the disulfide-reduced form of HO2sol that cannot be attributed to heme binding at the catalytic site. Further analysis revealed that while HO2sol binds one Fe(3+)-heme per monomer of protein under oxidizing conditions, disulfide-reduced HO2sol binds slightly more than two. Both Cys265 and Cys282 were identified as Fe(3+)-heme ligands, and His256 also acts as a ligand to the Cys265-ligated heme. Additionally, Fe(3+)-heme binds with a much weaker affinity to Cys282 than to Cys265, which has an affinity much weaker than that of the His45 binding site in the catalytic core. In summary, disulfide-reduced HO2 has multiple binding sites with varying affinities for Fe(3+)-heme.

Melanocortin-4 receptors expressed by cholinergic neurons regulate energy balance and glucose homeostasis.

Melanocortin-4 receptor (MC4R) mutations cause dysregulation of energy balance and hyperinsulinemia. We have used mouse models to study the physiological roles of extrahypothalamic MC4Rs. Re-expression of MC4Rs in cholinergic neurons (ChAT-Cre, loxTB MC4R mice) modestly reduced body weight gain without altering food intake and was sufficient to normalize energy expenditure and attenuate hyperglycemia and hyperinsulinemia. In contrast, restoration of MC4R expression in brainstem neurons including those in the dorsal motor nucleus of the vagus (Phox2b-Cre, loxTB MC4R mice) was sufficient to attenuate hyperinsulinemia, while the hyperglycemia and energy balance were not normalized. Additionally, hepatic insulin action and insulin-mediated suppression of hepatic glucose production were improved in ChAT-Cre, loxTB MC4R mice. These findings suggest that MC4Rs expressed by cholinergic neurons regulate energy expenditure and hepatic glucose production. Our results also provide further evidence of the dissociation in pathways mediating the effects of melanocortins on energy balance and glucose homeostasis.

PI3K signaling in the ventromedial hypothalamic nucleus is required for normal energy homeostasis.

Phosphatidyl inositol 3-kinase (PI3K) signaling in the hypothalamus has been implicated in the regulation of energy homeostasis, but the critical brain sites where this intracellular signal integrates various metabolic cues to regulate food intake and energy expenditure are unknown. Here, we show that mice with reduced PI3K activity in the ventromedial hypothalamic nucleus (VMH) are more sensitive to high-fat diet-induced obesity due to reduced energy expenditure. In addition, inhibition of PI3K in the VMH impaired the ability to alter energy expenditure in response to acute high-fat diet feeding and food deprivation. Furthermore, the acute anorexigenic effects induced by exogenous leptin were blunted in the mutant mice. Collectively, our results indicate that PI3K activity in VMH neurons plays a physiologically relevant role in the regulation of energy expenditure.

Direct insulin and leptin action on pro-opiomelanocortin neurons is required for normal glucose homeostasis and fertility.

Circulating leptin and insulin convey information regarding energy stores to the central nervous system, particularly the hypothalamus. Hypothalamic pro-opiomelanocortin (POMC) neurons regulate energy balance and glucose homeostasis and express leptin and insulin receptors. However, the physiological significance of concomitant leptin and insulin action on POMC neurons remains to be established. Here, we show that mice lacking both leptin and insulin receptors in POMC neurons (Pomc-Cre, Lepr(flox/flox) IR(flox/flox) mice) display systemic insulin resistance, which is distinct from the single deletion of either receptor. In addition, Pomc-Cre, Lepr(flox/flox) IR(flox/flox) female mice display elevated serum testosterone levels and ovarian abnormalities, resulting in reduced fertility. We conclude that direct action of insulin and leptin on POMC neurons is required to maintain normal glucose homeostasis and reproductive function.

Segregation of acute leptin and insulin effects in distinct populations of arcuate proopiomelanocortin neurons.

Acute leptin administration results in a depolarization and concomitant increase in the firing rate of a subpopulation of arcuate proopiomelanocortin (POMC) cells. This rapid activation of POMC cells has been implicated as a cellular correlate of leptin effects on energy balance. In contrast to leptin, insulin inhibits the activity of some POMC neurons. Several studies have described a "cross talk" between leptin and insulin within the mediobasal hypothalamus via the intracellular enzyme, phosphoinositol-3-kinase (PI3K). Interestingly, both insulin and leptin regulate POMC cellular activity by activation of PI3K; however, it is unclear whether leptin and insulin effects are observed in similar or distinct populations of POMC cells. We therefore used dual label immunohistochemistry/in situ hybridization and whole-cell patch-clamp electrophysiology to map insulin and leptin responsive arcuate POMC neurons. Leptin-induced Fos activity within arcuate POMC neurons was localized separate from POMC neurons that express insulin receptor. Moreover, acute responses to leptin and insulin were largely segregated in distinct subpopulations of POMC cells. Collectively, these data suggest that cross talk between leptin and insulin occurs within a network of cells rather than within individual POMC neurons.

Monitoring FoxO1 localization in chemically identified neurons.

The PI3K-Akt-FoxO1 pathway contributes to the actions of insulin and leptin in several cell types, including neurons in the CNS. However, identifying these actions in chemically identified neurons has proven difficult. To address this problem, we have developed a reporter mouse for monitoring PI3K-Akt signaling in specific populations of neurons, based on FoxO1 nucleocytoplasmic shuttling. The reporter, FoxO1 fused to green fluorescent protein (FoxO1GFP), is expressed under the control of a ubiquitous promoter that is silenced by a loxP flanked transcriptional blocker. Thus, the expression of the reporter in selected cells is dependent on the action of Cre recombinase. Using this model, we found that insulin treatment resulted in the nuclear exclusion of FoxO1GFP within POMC and AgRP neurons in a dose- and time-dependent manner. FoxO1GFP nuclear exclusion was also observed in POMC neurons following in vivo administration of insulin. In addition, leptin induced transient nuclear export of FoxO1GFP in POMC neurons in a dose dependent manner. Finally, insulin-induced nuclear export was impaired in POMC neurons by pretreatment with free fatty acids, a paradigm known to induce insulin resistance in peripheral insulin target tissues. Thus, our FoxO1GFP mouse provides a tool for monitoring the status of PI3K-Akt signaling in a cell-specific manner under physiological and pathophysiological conditions.

5-HT2CRs expressed by pro-opiomelanocortin neurons regulate energy homeostasis.

Drugs activating 5-hydroxytryptamine 2C receptors (5-HT2CRs) potently suppress appetite, but the underlying mechanisms for these effects are not fully understood. To tackle this issue, we generated mice with global 5-HT2CR deficiency (2C null) and mice with 5-HT2CRs re-expression only in pro-opiomelanocortin (POMC) neurons (2C/POMC mice). We show that 2C null mice predictably developed hyperphagia, hyperactivity, and obesity and showed attenuated responses to anorexigenic 5-HT drugs. Remarkably, all these deficiencies were normalized in 2C/POMC mice. These results demonstrate that 5-HT2CR expression solely in POMC neurons is sufficient to mediate effects of serotoninergic compounds on food intake. The findings also highlight the physiological relevance of the 5-HT2CR-melanocortin circuitry in the long-term regulation of energy balance.

Acculturation, social alienation, and depressed mood in midlife women from the former Soviet Union.

Level of acculturation has been linked to depressed mood in studies across culturally diverse immigrant groups. The purpose of this study was to determine the effects of acculturation, social alienation, personal and family stress, and demographic characteristics on depressed mood in midlife immigrant women from the former Soviet Union. Structural equation modeling showed that higher acculturation scores, measured by English language and American behavior, were indirectly related to lower scores for depressed mood. Higher acculturation levels promoted mental health indirectly by reducing social alienation and, subsequently, lowering family and personal stress, both of which had direct relationships to symptoms of depression. These findings support the ecological framework that guided our research and point to the importance of focusing on contextual factors in developing interventions for new immigrants.

SAP increases FynT kinase activity and is required for phosphorylation of SLAM and Ly9.

The free Src homology 2 (SH2) domain protein SAP, encoded by the X-linked lymphoproliferative disease gene SH2D1A, controls signal transduction initiated by engagement of the SLAM-related receptors in T and NK cells. Here we demonstrate that SAP is required for phosphorylation of both SLAM and Ly9 in thymocytes and peripheral T cells. Furthermore, in vitro protein interaction studies and yeast two-hybrid analyses indicated that SAP binds directly to FynT and Lck. While SAP bound to both the SH3 domain and to the kinase domain of FynT, SAP bound solely to the kinase domain of Lck. The existence of a strong interaction between SAP and the SH3 domain of FynT prompted us to study the role of SAP in modulating the activity of FynT. In vitro addition of SAP to the autoinhibited form of FynT caused a large increase in FynT catalytic activity. By contrast, the SAP mutant R78E, which is unable to bind to the FynT SH3 domain, did not increase FynT activity and also displayed a reduced adaptor function upon transfection into T cells. Our results demonstrate that SAP is an adaptor that bridges SLAM and Ly9 with Src-like protein tyrosine kinases (PTKs), and has the ability to activate FynT.