Sorafenib Is Contributing to Salvage Chemotherapy and Is Effective Given Alone for Maintenance in AML FLT3 ITD Patients Relapsing Post Allo Hematopoietic Stem Cell Transplantation

Normal karyotype AML patients with FLT3 ITD have a higher risk of relapse than those lacking this mutation (Estey EH, Am J Hematol. 2013). Our comparative genomic hybridization study (77 patients) showed that AML cases with as compared to those without FLT3 ITD had significantly lower number of amplifications or deletions (number of total CNV aberrations: 18±4 vs 51±8, p=0.003). The latter observation in concert with that of others (Thiede, Blood 2002) suggest that FLT3 ITD mutation if present in normal karyotype patients is a key player in the pathogenesis of leukaemia and targeting this mutation may be used successfully in FLT3 ITD positive patients relapsing post HSCT.

This was also the case in the two patients presented in this study.

Patient UPN 952, male, 53 years old, AML M4 (FAB), normal karyotype, received alloHSCT in 2 CR after completion of two lines of remission induction therapies (first: DA3+7 (Daunorubicin, Ara-C), HAM, high dose Ara-C; second: ICE (IDA, Ara-C, VP-16)) and then promptly transplanted. He relapsed 56 days after transplantation.

Patient UPN 938, female, 50 years old, AML, normal karyotype, received as an induction DA 3+7, and for consolidation HAM and high dose Ara-C and completed only one course of the maintenance therapy and transplanted in CR.

Both cases were transplanted from unrelated donors (10/10 HLA A, B, C, DR and DQ alleles matched), they received myeloablative conditioning (i.v. Busulfan and Cyclophosphamide) and Cyclosporin A as GvHD prophylaxis. At relapse they received salvage chemotherapy tailored to their biological performance (UPN 938 having Age Adjusted Charlson Comorbidity Index 3 received FLAG and UPN 952 with the index 9, ECOG 3, DA2+5). Both cases received in addition Sorafenib (two times 400 mg per day). The response was prompt and the marrow was free from blasts beginning from 11 day post chemotherapy. UPN 952 received as a maintenance only one course of 6-TG with low dose of Ara-C. Due to the substantial comorbidity and liver toxicity WHO3 further chemotherapy treatment was terminated. The patient was left only on Sorafenib (2 times 200 mg per day). UPN 938 was receiving the maintenance therapy (AML protocol) in 6 – 8 weeks intervals based on low dose Ara-C with 6TG or DNR and also Sorafenib (2 times 200 mg per day).

In both cases FLT3 signalling pathway (FLT3 Pathway Mutation PCR Array, SABiosciences, Qiagen) revealed a lack of any additional mutation at the check points in FLT3, KRAS, HRAS, NRAS, MEK1, PIK3CA, BRAF and PTEN genes. UPN 938 had in addition to FLT3 ITD mutation c.1807_1808insATGAATATGATCTCAAAT (p.K602_W603insYEYDLK) insertion which relevance was not so far describe. Sorafenib resistance mutations were not found.

The patients were on Sorafenib for 8 (UPN 938) and 9 months (UPN 952).

The course of UPN938 was uncomplicated. The second case showed mild aGvHD symptoms evolving into cGvHD (skin lesions and dry eye) slowed down with rapamicine.

Up to now the patients are in CR and free from FLT3 ITD. The main observation points:

- Sorafenib with chemotherapy tailored to the biologic performance of patients contributes to the efficient salvage in patients with relapsing FLT3 ITD positive AML post HSCT and is also effective given alone as a maintenance.

- Side effects were seen in one out of two patients likely associated with the blocking of VEGFR signalling transmission (hand foot skin rash, von Willebrandt factor activity – 388%).

Conclusion:

1. The use of multikinase inhibitor (Sorafenib) contributes effectively to salvage therapy in FLT3+ AML patients relapsing post alloHSCT

2. Sorafenib given alone is able to maintain long-lasting remission

3. Side effects are individually dependent

Supported by NBiR CellsTherpy grant and Byer Health Care