Introduction: Graft failure remains a major obstacle to the success of allo-HSCT. Rates of graft failure are reported to be 2% in recipients of HLA identical grafts, 9% in those with an unrelated donor, and up to 12.3% in those with an HLA-mismatched related donor (0-3 antigen mismatched). Graft failure is associated with high mortality due to prolonged cytopenia's leading to significant anemia, bleeding, and infection. Successful management of graft failure usually requires a second transplant to restore normal hematopoiesis. The selection of a preparative regimen presents a challenge in these patients who have recently undergone myelosuppressive therapy prior to the failed transplant maneuver. We have employed the use of a minimally myelosuppressive regimen consisting of a single dose of pentostatin with a low dose of total body irradiation (TBI) as conditioning prior to a second allogeneic transplant for patients who experienced primary graft rejection. Methods: Under an IRB-approved retrospective study, we describe 4 consecutive patients with graft failure after allogeneic stem cell transplantation, who received a re-conditioning regimen consisting of pentostatin and low-dose TBI prior to second allo-HSCT. The median age of patients was 38 years (23-51). The conditioning regimens of the first transplant were myeloablative doses of cyclophosphamide/rabbit ATG; busulfan/fludarabine rabbit ATG/; busulfan/fludarabine; and fludarabine/melphalan (Table 1). Median cell doses for the first transplant were 7.7 x 10E6 CD34+ cells/kg and 104 x 10E6 CD3+ cells/kg. Two patients had primary graft rejection and 2 patients had secondary graft rejection. Patients with secondary graft rejection had initial hematopoietic engraftment of neutrophils on a median of 21 days and platelets on a median 61 of days post-transplant with subsequent declines in peripheral blood counts and chimerism studies showing loss of donor cell engraftment. The donor for the second transplant was the same in one patient and different in three patients and included a HLA-matched sibling in 2/4 patients and HLA-matched unrelated donor (URD) in 2/4 patients. One patient had two transplants from the same donor followed by a third transplant from a different HLA matched sibling donor. Conditioning for the second transplant in these cases consisted of pentostatin 4 mg/m2 as a single dose on day -3 and two fractions of 200 cGy TBI on days -2 and -1 as shown in Table 2. Results: Patients underwent the second (or third) donor allogeneic transplant at a median of 99 days following the first transplant. The second donor allograft contained a median of 9.6 x 10E6 CD34+ cells/kg and 390 x 10E6 CD3+ cells/kg. All recipients of the pentostatin-TBI conditioning regimen engrafted following transplantation of allogeneic stem cells (Table 2). Engraftment following the second transplant (or third transplant, in patient #1) occurred at a median of 22 days for neutrophils and 54 days for platelets, and all patients achieved 100% myeloid and lymphoid chimerism. Patients did not experience VOD/SOS or have severe mucositis, enteritis, or pulmonary toxicity, and were hospitalized a median of 39 days from the second transplant. All four patients achieved normal blood counts following the second transplant. One patient died unexpectedly of an apparent infection following full donor hematopoietic reconstitution. Three of the four patients undergoing a second transplant using pentostatin/TBI conditioning are alive without evidence for disease relapse or graft rejection at a median follow-up of 3.5 years, with none of these patients experiencing severe acute or chronic GvHD. Conclusion: Single dose pentostatin combined with low-dose TBI represents an effective and well-tolerated conditioning regimen that facilitates engraftment of a second allogeneic transplant in patients who experienced primary or secondary graft rejection. The enhanced therapeutic efficacy of this reduced-intensity regimen that allowed consistent donor-derived hematopoietic engraftment after initial allo-graft rejection warrants further study. Disclosures Langston: Astellas Pharma: Other: Research Support; Incyte: Other: Research Support; Jazz Pharmaceuticals: Other: Research Support; Chimerix: Other: Research Support; Takeda: Other: Research Support; Kadmon Corporation: Other: Research Support; Novartis: Other: Research Support; Bristol Myers Squibb: Other: Research Support. Waller:Pharmacyclics: Other: Travel expenses, Research Funding; Cerus Corporation: Other: Stock, Patents & Royalties; Chimerix: Other: Stock; Cambium Oncology: Patents & Royalties: Patents, royalties or other intellectual property ; Amgen: Consultancy; Kalytera: Consultancy; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. OffLabel Disclosure: the use of pentostatin as part of a conditioning regimen

e14056 Background: Agomelatine is a melatonin receptor agonist (MT1 and MT2) and a 5-HT2C receptor antagonist. Melatonin is a lipophilic compound that is capable of binding to cell surface receptors, cytosolic sites (calmodulin), and directly to nuclear DNA binding sites (nuclear receptors RZR/RORα). Its direct antioxidant, antimitotic, antiestrogenic, prodifferentiating and antimetastatic effects have been well characterized. Nitric oxide (NO) is an inorganic free radical gas synthesized from L-arginine by a family of isoenzymes called NO synthases. Two of these are constitutively expressed and a third is inducible by immunological stimules. The NO released by the constitutive enzymes acts as an important signaling molecule in the cardiovascular and nervous systems and NO released by the inducible NO synthase (iNOS) is generated for long periods, by cells of the immune system among others, and has been shown to be cytostatic/cytotoxic for tumor cells and a variety of microorganisms. Methods: We have studied oncostatic/citostatic influence by ATP-TCA method of agomelatine and agomelatine + trastuzumab solution on the cellular cultures Her2/neu (+), MT1 and MT2 receptor (+) mammary ductal adenocarcinoma (17 cases). Data of ATP-TCA test in healthy patients breast’s cellular cultures with only trastuzumab were used as control. In parallel, we have studied expression of enzyme universal nitric oxide synthase (u-NOS) in cellular cultures of mammary ductal adenocarcinoma all three cells lines using Western blot method. The findings were compared to the data of u-NOS expression in healthy patients breast’s breast cellular cultures. Results: The study demonstrated that influence of citostatic effect of only agomelatine by ATP-TCA method are increased by 32.5% and citostatic effect of agomelatine + trastuzumab by ATP-TCA method also are increased by 45% in compared to control. Expression of universal nitric oxide synthase (u-NOS) is increased in case of mammary ductal adenocarcinoma by 14.2% in case only agomelatine and by 26.7% in case agomelatin + trastuzumab compared to control. Conclusions: Results of this research describe the positive role of agonists melatonin receptors (agomelatin) in the treatment previously treated and after progressed breast cancer (while this mechanism in details is unknown for us) and increased expression of NOS indicate the possibly augmentation sensitivity the cells lines for the citostatics medicines.

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e12581 Background: According to WHO data, Breast Cancer is the most prevalent malignancy in women. The biological role of Melatonin in the etiology and pathogenesis of the tumour disease has already been approved by a number of research studies. The purpose of our investigation was the assessment of features of Melatonin receptor circadian expression in circulating tumour cells of breast cancer (CTCs). Methods: We observed 34 patients (aged 36-68) with breast cancer (various immunophenotypes). CTCs were separated from patients’ venous blood every third day, in 02:00-04:00 pm and in 02:00-04:00 am intervals. The cells were taken from each patient 4 times. On CTCs, MT1 – receptor expression was assessed using immunocytochemical method. Results: Results of the study revealed that Melatonin receptor expression in breast cancer patients is characterised by the noticable circadian rhythmics. MT1–receptor expression peak by CTCs was detected at 02:00-04:00 am i.e. at night. The less aggressive tumor the higher is the extent of the receptor expression (density). Respectively, in hormone dependent and Her2/neu (negative) tumors the highest expression of the MT1–receptor occurs in hormone dependent and Her2/neu(positive) tumors–medium expression and in triple negative breast Cancer (TNBC) cells–the lowest expression, while in some TNBC–circulating tumor cells MT1 receptor expression has not been detected at all. Conclusions: Hence, based on our the results, we can conclude that Melatonin as the expression of main biochemical marker receptors of bio-rhythms in breast cancer cells, has highly expressed chronobiological nature and directly correlates with histological types of tumor, that provides conditions for the development of new chronotherapeutic strategies in breast cancer treatment.

e15678 Background: Primary liver cancer (HCC) treatment is one of the priority issues of clinical oncology due to inefficiency and quantitative lack of medicines. The goal of our research was to perform treatment of Primary Liver Cancer, based on chronobiological mechanisms, assessment of treatment efficiency and advantage over the standard regimen. Methods: A total of 21 patients with HCC participated in the study. The treatment was performed by Liposomal Cisplatin. Assessment of cancer cells sensitivity to platinum group medicines was performed using RT-PCR method by expression of DNA methyltransferase I gene. During 24 hours, with 2-hour intervals, circulating tumor cells (CTC) were taken from peripheral venous blood. At the end, in all samples circadian regimens of DNA methyltransferase I gene expression were studied. According to obtained results, the circadian peak of gene expression was registered at 02:00-04:30 am time interval. Results: According to the study design of the 21 patients 12 ones received treatment based on chronotherapy regimens (investigated group, infusions were made at 02:00-04:30 am), 9 patients received treatment with standard regimen (control group, infusion was performed at 10:00-12:00 am). Infusions were performed according to the protocol with 1 week intervals for 9 weeks (a single infusion dose 150mg/m2). The treatment efficiency was evaluated 9 weeks later by the following parameters: AFP serum level and computer tomography of the liver. Results of the study demonstrated significant differences in treatment efficacy. During chemotherapy performed in chronotherapy regimen in patient's blood plasma, the AFP concentration decreased on average by 36.5% compared to the initial value, however in the control group the AFP concentration decreased on average by 13.7%. By CT positive dynamics was detected in both groups, but with significant advantage in case of chronotherapy regimen, size reduction of tumor growth by 27.1% on average was associated with fibrous transformation and prominent decrease of vascularization was found. In the control group, size reduction of the tumour growth was seen, however only by 6.3% on average. Patients clinical condition as well as CBC data differed with significant prevailing in case of chronotherapy. Conclusions: Obtained results confirm high clinical significance of chronobiological features of gene expression in antitumour therapy as well as importance of the development of new, up-to-date protocols for HCC – highly aggressive tumour therapy based on chronotherapy principles.