Citations

Abstract Introduction: Amphiregulin (AREG) is an epidermal growth factor receptor (EGFR) ligand that can restore integrity to damaged intestinal mucosa in murine models of acute graft-versus-host disease (aGVHD). We previously described AREG as a circulating biomarker of late-onset aGVHD, but its relevance combined with clinical risk factors has not yet been tested in a large cohort of patients with aGVHD occurring prior to day 100 post-transplant. We therefore tested samples from two aGVHD first-line treatment trials, Blood and Marrow Transplant Clinical Trials Network (BMT CTN) 0302 and 0802, and identified a clinically relevant threshold level of circulating AREG at aGVHD onset. We then investigated whether incorporating AREG into the refined Minnesota Risk Score could further risk-stratify patients. Patients and Methods: Blood samples were obtained at the onset of systemic aGVHD treatment within BMT CTN 0302 (serum) and BMT CTN 0802 (plasma). All patients with response data and samples for analysis from both trials were included (N=251). We determined the association of AREG with clinical outcomes, including risk stratification by the refined Minnesota criteria, day 28 complete/partial response (CR/PR) to first-line therapy, 2-year overall survival (OS) and 6-month and 2-year non-relapse mortality (NRM). We investigated the effect of AREG on clinical endpoints per a doubling in the value of AREG, defined a clinically relevant threshold level in the AREG values using two-fold cross-validation, and confirmed the clinical relevance of this cut-point in independent samples (N=92) from pooled from drawn from the Chronic GVHD Consortium and the Mount Sinai Acute GVHD International Consortium (MAGIC). Results: In patients enrolled in BMT CTN 0302/0802, AREG levels were 1.7-fold higher in patients with Minnesota high-risk (HR) compared to standard-risk (SR) aGVHD (HR median 53.4 vs SR 31 pg/ml, p<0.01). Every 2-fold increase in AREG was associated with a 33% decrease in the likelihood of day 28 CR/PR (odds ratio [OR] 0.67, p<0.01, table). Clinical factors alone, as determined by the refined Minnesota Risk Score, were associated with day 28 CR/PR (p=0.02, table). Adding AREG to the Minnesota Risk Score could further risk-stratify patients. Minnesota SR patients with elevated AREG ≥ 33 pg/mL showed a 59% lower odds of day 28 CR/PR than SR patients with low AREG (OR 0.41, p=0.02). Patients with Minnesota HR aGVHD with AREG ≥ 33 pg/mL had the worst outcomes, with an 82% lower odds of day 28 CR/PR in comparison to HR with low AREG (OR 0.18, p<0.01). High AREG was associated with worse OS and NRM in both Minnesota SR (hazard ratios 2-year OS 2.3, p<0.01 and 6 month NRM 2.95, p=0.01, respectively) and HR patients (hazard ratios 2-year OS 3.35, p<0.01 and 6-month NRM 9.38, p<0.01 respectively, figure). Finally, in independent samples from the Chronic GVHD Consortium/MAGIC we confirmed that high AREG was associated with worse day 28 CR/PR (55.2% vs. 79.4%, p=0.02) and significantly worse 6-month survival after the onset of aGVHD (57.1% vs. 82.5%, p=0.01). Conclusion: AREG is elevated in patients with poor aGVHD outcomes and adds to the accuracy of risk stratification when combined with the refined Minnesota Risk Score. AREG ≥33 pg/mL at aGVHD onset is associated with lower day 28 CR/PR and higher mortality in samples from 4 multicenter cohorts. The mechanism of elevated circulating AREG in severe aGVHD is not yet known, although we hypothesize the degree of AREG elevation reflects the intensity of immune-mediated tissue injury resulting in AREG release. With accumulating evidence of altered EGFR ligands in aGVHD, further investigation into epithelial repair pathways involving AREG may lead to new adjunctive therapies to overcome poor steroid response in high-risk aGVHD. Disclosures Holtan: Incyte: Other: One-time advisory board member. Khera: Novartis: Consultancy. Lee: Mallinckrodt: Honoraria; Amgen: Other: One-time advisory board member; Bristol-Myers-Squibb: Other: One-time advisory board member; Kadmon: Other: One-time advisory board member. Chen: Immudex: Research Funding. Arora: Takeda Oncology: Consultancy. Flowers: Pharmacyclics: Consultancy. Cutler: Pfizer: Consultancy; Kite: Consultancy; Incyte: Consultancy; Bristol-Myers Squibb: Consultancy; Pharmacyclics: Consultancy; Astellas: Consultancy. Jagasia: Janssen: Consultancy, Research Funding; Therakos: Consultancy, Research Funding; Mallinckrodt: Consultancy. Hexner: Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding. Levine: Novartis Pharmaceuticals Corporation: Membership on an entity's Board of Directors or advisory committees. MacMillan: Magenta Therapeutics: Research Funding.

Abstract The optimal source of donor hematopoietic stem cells (HSC) is controversial. Granulocyte colony stimulating factor (G-CSF) mobilized peripheral blood (G-PB) has replaced bone marrow (BM) as the most common allograft source in adults but is associated with donor morbidity and higher rates of chronic graft versus host disease (GVHD) compared to BM. The CXCR4 antagonist plerixafor (Px) mobilizes HSC into the PB (Px-PB) faster than G-CSF and preliminary data suggest both quantitative and qualitative differences in allograft content that may impact clinical outcomes. We sought to assess the efficacy and safety of transplanted allografts collected following mobilization with Px alone in HLA-identical sibling transplantation. This was a Phase II, two-strata, multi-center prospective trial (NCT01696461) to evaluate Px-PB allografts prior to reduced intensity conditioning (RIC) and myeloablative conditioning (MAC) based hematopoietic cell transplantation (HCT). Patients aged 18-65 years with an HLA-ID sibling donor and a hematological malignancy suitable for HCT were eligible. The primary objective was to determine the proportion of donors whose cells could be successfully mobilized and collected with a sufficient CD34+ cell dose using Px as the sole mobilizing agent. Px mobilization was considered successful if ≥ 2.0x10^6 CD34+ cells/kg recipient weight were collected in no more than two leukapheresis (LP) collections. All donors receiving Px were included in the analysis of the primary objective based on the intention-to-treat principle. Secondary objectives included the incidence of acute and chronic adverse events in donors, rates of hematopoietic engraftment, donor chimerism, rates of acute and chronic GVHD, non-relapse mortality (NRM), progression free survival (PFS) and overall survival (OS) for the recipients. From July 2013 to December 2014, 64 donor/recipient pairs were enrolled at 12 centers. Donors received Px at 240μg/kg subcutaneously 4 hours prior to LP. LP was performed processing at least 4X blood volume for up to two consecutive days (a third day was allowed for low CD34+ cell yields after 2 LP procedures) to achieve a target CD34+ cell dose of ≥ 4.0 x 10^6/kg recipient weight with a minimum goal of ≥ 2.0 x 10^6/kg. All allografts were cryopreserved. GVHD prophylaxis included cyclosporine or tacrolimus in combination with methotrexate, mycophenolate mofetil, or sirolimus. G-CSF was given routinely post HCT only to MAC recipients. Patient demographics are provided in Table 1. The median donor age was 56 years (18-65). 64% of the donors were male. Donors underwent one (23%), two (72%), or three (5%) LP procedures. 63 of 64 (98%) donors achieved the primary objective. The median total CD34+ cell dose/kg recipient weight collected within 2 days was 4.6 (0.9-9.6). Maximal donor toxicity following Px injection and LP was grades 0 (30%), 1 (52%), 2 (17%), and 3 (2%). Bloating, flatulence, abdominal pain, headache, paresthesisas, injection site reaction, and dizziness were the most commonly observed toxicities. Bone pain was not observed. The one grade 3 toxicity was a vasovagal episode felt related to LP and unlikely to Px. Toxicities typically resolved within a week of LP. The median follow up is 6.3 months. Median days to ANC (>0.5 x10^9/L) and Platelet count (>20 x 10^9/L) recovery were 13.5 (10-148) and 19 (1-76) after MAC and 14.5 (0-25) and 18 (0-141) after RIC, respectively. The cumulative incidence of acute GVHD grades 2-4 and 3-4 at day 100 were 47% (95% CI: 30-64) and 9% (95% CI: 2-22) after MAC and 19% (95% CI: 6-38) and 5% (95% CI: 0-18) after RIC. Probability of NRM at day 100 was 4% (95% CI: 0-13) and 0% after MAC and RIC, respectively. The probability of OS at day 100 was 97% (95% CI: 88-100) and 90% (95% CI: 78-98) after MAC and RIC, respectively. In conclusion, this is the first multi-center trial to demonstrate that as an alternative to G-CSF, Plerixafor rapidly, safely, and effectively mobilizes sufficient numbers of CD34+ cells from HLA-ID sibling donors for HCT following both RIC and MAC regimens. Engraftment was generally prompt and early results of secondary endpoints in recipients are encouraging. Longer follow-up and more extensive analysis of donor allografts and recipient outcomes will be presented at the time of the meeting. Research support was provided in part by Genzyme, a Sanofi Company. Table 1. Characteristics of recipients Table 1. Characteristics of recipients Disclosures Chen: Bayer: Consultancy, Research Funding. Devine:Genzyme: Research Funding.

Abstract Plerixafor, a direct antagonist of CXCR4/stromal-derived factor 1, can safely and rapidly mobilize allografts without the use of granulocyte colony-stimulating factor (G-CSF). We conducted a phase 2, multicenter, prospective study of plerixafor-mobilized HLA-identical sibling allografts for allogeneic hematopoietic cell transplantation in recipients with hematological malignancies. Donors (n = 64) were treated with subcutaneous plerixafor (240 µg/kg) and started leukapheresis (LP) 4 hours later. The primary objective was to determine the proportion of donors who were successfully mobilized: defined as collection of ≥2.0 × 106 CD34+ cells per kilogram recipient weight in ≤2 LP sessions. Recipients subsequently received reduced intensity (RIC; n = 33) or myeloablative (MAC; n = 30) conditioning. Sixty-three of 64 (98%) donors achieved the primary objective. The median CD34+ cell dose per kilogram recipient weight collected within 2 days was 4.7 (0.9-9.6). Plerixafor was well tolerated with only grade 1 or 2 drug-related adverse events noted. Bone pain was not observed. Plerixafor-mobilized grafts engrafted promptly. One-year progression-free and overall survivals were 53% (95% confidence interval [CI], 36% to 71%) and 63% (95% CI, 46% to 79%) for MAC and 64% (95% CI, 47% to 79%) and 70% (95% CI, 53% to 84%) for RIC recipients, respectively. Donor toxicity was reduced relative to G-CSF mobilized related donors. This is the first multicenter trial to demonstrate that, as an alternative to G-CSF, plerixafor rapidly and safely mobilizes sufficient numbers of CD34+ cells from matched sibling donors for HCT. Engraftment was prompt, and outcomes in recipients were encouraging. This trial was registered at clinicaltrials.gov as #NCT01696461.