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Background Improving strategies for patients (pts) with relapsed/refractory (R/R) Hodgkin lymphoma (HL) who fail stem cell transplantation (SCT) or are unsuitable for the procedure remains an essential need. Lenalidomide and bendamustine are active and well tolerated as single agents in recurrent HL, with overall response rates (ORR) of 30% to 53% [Fenhinger, 2012; Corazzelli, 2012; Moskowitz, 2012].These agents independently frame different targets on tumor and microenvironment cells and may cooperate to override disturbed immunologic pathways and circumvent drug resistance in HL. In a Bayesian, multi-center, open label phase 1/2 study, we investigated for safety and efficacy the combination of continuous lenalidomide with weekly bendamustine (ClinicalTrials.gov # NTC01412307). Methods The study aimed at defining the optimal daily dose of continuous lenalidomide (10, 15, 20 or 25 mg) as combined, in a 28-day cycle, to weekly fixed-dose bendamustine (60 mg/m2; d 1, 8, 15). The dose-finding algorithm proceeded in cohorts of 3 pts, based on anticipated efficacy and toxicity pairs of probability (Thall & Cook, Biometrics 2004). Trade-offs between response [Cheson 2007 criteria] and dose-limiting toxicity [CTCv3.0 grade (G) >3 lasting >2 weeks] were assessed after 2 cycles (day +56) and pts were planned to receive up to 6 total courses, unless progression or unacceptable toxicity occurred. ORR and progression-free survival (PFS) were additional endpoints. Results Thirty-six pts (69% male) with a median age of 31 yrs (r 19-75) were enrolled. The median number of prior therapies was 4 (r 1-9) and the median time from upfront treatment was 24 mo.s (r 7-118). Twenty-six pts (72%) had primary refractory disease after ABVD, 16 pts (44%) failed prior SCT [single (n=7) or tandem (n=3) ASCT, tandem ASCT/alloSCT (n=6)]. Fifteen pts (42%) had previously received a median of 5 cycles (r 2-8) of brentuximab vedotin (BV) and 3 pts were already given bendamustine (>3 courses). Overall, 23 pts (64%) were refractory to most recent therapy. Eff/Tox trade-offs at cycle 2 showed that 73% of pts had response w/o toxicity, 19% had no response w/o toxicity, 6% had response with toxicity and 2% had no response with toxicity. With such Eff/Tox profiles, the study algorithm did not prompt any dose escalation for lenalidomide after the first 18 pts and the initial dose level (10 mg) was adopted for the expansion phase. A total of 156 LeBen cycles were administered, and pts received a median of 4 courses (r 1-6). Overall, 16 cycles were delayed due to G3/G4 thrombocytopenia (n=6), G4 neutropenia (n=3), G3 pneumonia (n=3), G3 respiratory infection (n=2), G2 phlebitis (n=1), G2 supraventricular arrhythmia (n=1). Two patients discontinued treatment, while in PR and CR after 4 courses, due to protracted (>2 weeks) thrombocytopenia. No G4 extra-hematological toxicity was observed. The complete response (CR) rate was 44% (16/36) with an ORR of 75% (27/36; 95% CI, 59-86). Notably, substantial CR and PR rates were achieved after LeBen regardless of primary refractoriness, SCT and BV failure (Table). Most CRs (14/16) were obtained within the first 4 cycles; 6 responders (4 CRs and 2 PRs) underwent SCT. Median PFS was 3.2 mo.s (r 1.5-5.4) for pts with progressive (PD) or stable disease (SD) and 11.4 mo.s (r 4-31) for those achieving CR/PR. Median overall survival for the entire cohort was 24 mo.s. Overall, complete responders (including 6 pts consolidated with SCT) had a 2-year disease-free survival of 41% (median, 14.3 mo.s). Conclusions The innovative schedule of the Leben combination is safe, yields high response rates in heavily pretreated and primary refractory HL pts, including SCT and BV failures, and steps over the 'single agent' activity of its components. Due to its immunomodulatory potential the Leben platform is amenable to further upgrading through lenalidomide maintenance, combination with immune checkpoint inhibitors and BV. | Responses no. (%) | All pts | Refractory to upfront therapy | Refractory to most recent therapy | Failure after SCT | Failure after ASCT | Failure after AlloSCT | Failure after BV | Failure after SCT and BV | Failure after bendamustine | No BV | | ------------------------ | ------- | ----------------------------- | --------------------------------- | ----------------- | ------------------ | --------------------- | ---------------- | ------------------------ | -------------------------- | ------- | | (n=36) | (n=26) | (n=23) | (n=16) | (n=10) | (n= 6) | (n=15) | (n=8) | (n=3) | (n=21) | | CR | 16 (44) | 11 (42) | 8 (35) | 8 (50) | 6 (60) | 2 (33) | 5 (33) | 3 (37) | | 11 | | PR | 11 | 8 | 9 | 4 | 2 | 2 | 4 | 2 | | 7 | | SD | 2 | 2 | 2 | 1 | | 1 | 1 | 1 | 1 | 1 | | PD | 7 | 5 | 4 | 3 | 2 | 1 | 5 | 2 | 2 | 2 | | CR+PR | 27 (75) | 19 (73) | 17 (74) | 12 (75) | 8 (80) | 4 (66) | 9 (60) | 5 (62) | | 18 (86) | Table 1. Efficacy results Disclosures Pinto: Takeda, Celgene, Roche, TEVA: Honoraria; Takeda: Research Funding. Zinzani: Takeda: Membership on an entity's Board of Directors or advisory committees; JJ Gilead: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees.

Background: Given the consistent antitumor activity and favorable toxicity profile in heavily pretreated patients, BDM represents a suitable platform for combination with target-based agents in the setting of recurrent HL. The anti-CD30 antibody-monomethyl auristatin E (MMAE) conjugate brentuximab vedotin (BV) appears a most valuable candidate by coupling an impressive clinical activity with the lack of serious overlapping toxicities with BDM. While the combination of BDM and BV is being evaluated in Phase II studies, no information is available as to possible mechanisms through which BDM may regulate the antitumor efficacy of BV towards HL cells. Methods: We evaluated the effects of acute and extended exposure to BDM on CD30 expression and sensitivity to the cytotoxic activity BV in the HL cell line L1236. Cells were cultured in the presence of BDM at its IC50 for different time points of acute exposure. Through continuous exposure to increasing concentrations (25.0, 50.0, 75.0, 100 micromol/L) of BDM, we then performed a serial in vitro selection for BDM-resistant (R) L1236 cell clones and determined their CD30 expression by flow cytometry, qRT-PCR, and Western analysis. Results: Acute exposure to BDM (48 to 72 hrs) of L1236 cells led to a sizeable upregulation of CD30 as shown by flow cytometry. This effect was unsustained since CD30 intensity returned to baseline levels upon culturing in BDM-free medium for one week. Expression of other surface antigens, i.e. HLA-DR, was unaffected by BDM while acute exposure to doxorubicin and other cytotoxic drugs did not modify the CD30 expression. We established four L1236-derived cell clones (R25, R50, R75 and R100) able to proliferate across the different concentrations of BDM with growth/viability curves superimposable to native cells. Clonal identity among clones and with parental cells was confirmed by sequencing of V3-21 (FR2/FR3) and JH3-JH4 Ig DNA regions. All R-clones displayed an up to 900% increase in CD30 median fluorescence intensity, relative to native L1236 cells (Figure 1A). The sustained CD30 upregulation was confirmed by qRT-PCR and Western blotting since R-clones expressed up to 10-fold higher levels of CD30-specific mRNA and CD30-specific 120 kDa components as compared to parental cells. To rule out a general upregulation of surface molecules as a result of the chronic exposure to BDM we evaluated the expression of other surface antigens. As opposed to CD30, HLA-DR and PDL-1 relative transcript levels and cell surface expression were significantly reduced in R-cells. Intriguingly, BDM-induced CD30 upregulation was specific to L1236 cells since extended exposure to BDM did not modify expression levels of CD30 in other lymphoma cell types (SUDHL1, JEKO). BDM-induced CD30 overexpression significantly enhanced the sensitivity of HL cells to the cytotoxic effects of BV. MTS assay showed the IC50 of R100 cells to BV shifted to 0.21 ± 0.06 mcg/mL (48 hrs) and 0.19 ± 0.05 mcg/mL (72 hrs) vs. 3.16 ± 0.75 mcg/mL (48 hrs) and 3.87 ± 0.68 mcg/mL (72 hrs) of parental cells, a 15- and 20-fold increase, respectively (p Conclusions: Whileacute exposure to BDM induced a transient upregulation of CD30, extended exposure to the agent resulted in the selection of L1236 subclones with a stable overexpression of surface CD30 and reduced levels of HLA-DR and PDL-1. Upregulation of CD30 was associated with a significantly enhanced sensitivity to cytotoxic effects of BV. Translated into a clinical context these findings suggest that HL patients progressing upon BDM treatment may turn exquisitely sensitive to BV and prompt the exploration of a sequential treatment with BDM and BV in late and earlier disease phases. Results also provide a mechanistic insight as to the efficacy of the BDM-BV combination in HL, highlighting non-overlapping resistance pathways between BDM and MMAE. BDM-induced selection of CD30hi, HLA-DRlow/PDL-1low tumor cell clones might be relevant to the design of novel treatment strategies for HL based on the combination of BDM with BV and anti-PD1/PDL-1 antibodies. Figure 1. Expression of CD30 and HLA-DR in parental (L1236) and BDM-resistant (R) HL cells Figure 1. Expression of CD30 and HLA-DR in parental (L1236) and BDM-resistant (R) HL cells Figure 2. Sensitivity to BV of parental (L1236) and BDM-resistant (R100) HL cells Figure 2. Sensitivity to BV of parental (L1236) and BDM-resistant (R100) HL cells Disclosures Pinto: Takeda: Research Funding; Takeda, Celgene, Roche, TEVA: Honoraria.

Abstract 5168 Background: Myeloproliferative neoplasms (MPNs) are a group of diseases characterized by clonal expansion of single or multiple lineages of myeloid subset (i.e. granulocytic, erythroid, megakaryocytic and mast cell). Since 2008, the WHO included the detection of JAK2 mutations (the common V617F and the less common exon 12 mutations), into the diagnostic criteria of MPNs. The specific pathogenic implication of JAK2 mutations in MPNs is still under investigation. Preliminary data emerging from the treatment of Idiopathic Myelofibrosis patients with JAK2 inhibitors have shown only clinically significant benefits (improvement of splenomegaly and constitutional symptoms) but not a clear evidence of disease-modifying activity. Several techniques (e.g. ASO-PCR, ARMS-PCR, Direct sequencing, HRM, DHPLC, etc) have been used to detect the JAK2 V617F mutation, but all of them were low sensitive and time-consuming. We developed a PNA-clamping competitive PCR assay able to detect JAK2 V617F mutation with a very high level of sensitivity and specificity. Methods: In order to promote the selective amplification of the JAK2 V617F mutant allele, a specific PNA oligonucleotide, full matching with the wild-type (wt) sequence of the portion of JAK2 gene containing the V617F mutation, was designed to compete with the reverse primer used in the PCR assay. It was experimentally demonstrated that a PNA concentration of 6 μmol/L occurred for the complete clamping of 100 ng of wt genomic DNA used as template for the PCR reaction. The sensitivity of the assay was determined by a serial dilution (100% through 0.01%) of genomic DNA containing JAK2 V617F mutation, obtained from HEL cell line, with wt DNA obtained from healthy donors. The specificity of PCR products was assessed by sequencing in both forward and reverse directions. The thermal dissociation profile of PNA/DNA and DNA/DNA duplexes was studied by monitoring the Enthalpy as function of the temperature (range 20–100°C), with an heating/cooling rate of 1°C/min. Results: PNA-clamping competitive PCR was able to detect JAK2 V617F mutation with a sensitivity of 0.01%. Thermodynamic studies clearly showed that the melting temperature (Tm) of fully matched PNA/DNA duplex is always higher than Tm of the corresponding DNA/DNA duplex. The enthalpy values for the hybrid PNA/DNA are always greater than the corresponding DNA/DNA duplex and a single mismatch has an energetic cost higher in a PNA/DNA than in DNA/DNA duplex. This energetic cost is more evident in the melting temperature with a ΔTm of 16°C and 7°C for the PNA/DNA and DNA/DNA duplex, respectively. In the PCR assay the PNA complementary to the JAK2 wild type sequence strongly compete with the primer resulting in a complete knock out of the wild type allele. In a blind screening of samples obtained from 308 MPN patients, PNA clamping competitive PCR was able to detect JAK2 V617F mutation in 61.4% cases of Polycythemia Vera, 54.4% of Essential Thrombocythemia, 57.9% of Idiopathic Myelofibrosis and in 21.4% of Ph negative-MPNs, respectively. In 40 unselected patients, PNA clamping PCR results were confirmed by other techniques such as ASO-PCR, ARMS-PCR and direct sequencing. Conclusions: The PNA-clamping competitive PCR assay could be used as convenient, high-sensitive and reliable diagnostic test for detection of JAK2 V617F mutation both on genomic DNA and cDNA samples. As suggested from the thermodynamic studies, a similar technique could be developed for the detection of any known single point mutation, widely contributing to the improvement of molecular diagnostic tests usable in clinical practice. Disclosures: No relevant conflicts of interest to declare.

Abstract 2437 Clinical course in individual CLL patients (pts) is highly heterogeneous. Several pts show an indolent disease and other experience an aggressive course rapidly succumbing to disease-related events. Different biomarkers have been developed to identify pts with evolving disease but their application is mostly limited to clinical trials. It has been shown that measurement of clonal serum free light chains (sFLC) levels, through a straightforward assay validated for plasma cell disorders, could independently identify CLL pts with progressive disease. By analyzing the largest cohort of CLL pts ever reported, we wished to: i) determine the independent predictive value of sFLC abnormalities in the context of established biomarkers; ii) define the predictive hierarchy of these markers; iii) incorporate sFLC into a novel prognostic system. Cryopreserved sera at diagnosis from 449 untreated pts (282 males and 167 females, median age 65 yrs; r 33–89) were collected for analysis at two reference laboratories. After quantization (Freelite, The Binding Site, Ltd., UK) of sFLC k and l levels (r, k: 3.3–19.4 mg/mL; l: 5.71–26.3 mg/mL), their ratio was calculated as sFLC k/l (r: 0.26–1.65). An abnormal sFLCk/l was found in 150/449 cases (132 k/18 l). A significant correlation emerged between sFLCk/l and CD38, ZAP70, unmutated IgHV and unfavourable FISH but not with Binet stage (Table). At a median follow up of 3 yrs (r 1–20), 149 of 449 pts were treated due to progressive disease (NCI Guidelines). Treatment-free survival (TFS) was significantly shorter (p60.6 mg/mL (HR=2.5, C.I. 2.6–3.9), remained the strongest independent predictor of TFS together with ZAP70 (HR=2.8, C.I. 1.8–4.6) and stage (HR=2.5, C.I. 1.6–3.8), while CD38 and IgVH status lost their predictive power. Most intriguingly, it emerged that sFLCk/l is irrelevant in predicting TFS if sFLCk+l is above cut-off and that cytogenetic risk remains significantly associated with sFLCk+l (P=0.047) but not FLCk/l. sFLCk+l retained an independent association with TFS together with cytogenetics, ZAP70 and stage. A novel prognostic model was then constructed with 1 point for each of these unfavorable marker and a score given by their sum. On 260 pts scores were: 104=0, 79=1, 56=2, 19=3, 4=4. The 3 year probability of avoiding treatment was 94.8%, 84.5%, 61.6% and 21.1% for pts scoring 0, 1, 2 and 3+4, respectively (P sFLC k/l in 449 untreated CLL pts Table 1. Death in complete remission by year sFLC k/l P Normal (%) Abnormal (%) CD38 − 234 (70.9) 96 (29.1) Disclosures: Amoroso: The Binding Site, LtD: Consultancy.