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in at least some of immune thrombocytopenia ( itp ) patients , thrombocytopenia is worsened by inappropriately low levels of platelet production , unable to compensate for the increased peripheral immune - mediated destruction of platelets . until recently ,
management of itp adult patients with platelet counts < 3010/l and/or bleeding signs has relied upon the use of drugs or procedures ( i.e. splenectomy ) aimed at decreasing b - cell and t - cell immune - response to autologous platelets and megakariocytes .
the availability of thrombopoietin - receptor agonist ( tpo - ra ) has offered new opportunities for treating adult itp patients acting on megakariocyte survival and production of platelets .
thrombopoietin - receptor agonist increase thrombopoiesis activating the c - mpl receptor on bone marrow megakariocytes , thus providing an additional stimulus to increase their survival and platelet production .
response rates up to 90% in long - term follow - up studieshave been reported with both romiplostim and eltrombopag .
however , platelet counts usually return to pretreatment levels upon discontinuation of treatment and long - term , if not life - long , administration was envisioned in order to maintain effective thrombopoiesis . in recent years sporadic patients
have been reported as being able to discontinue treatment with either romiplostim or eltrombopag without relapsing off - therapy .
most studies were not designed to assess feasibility of tpora discontinuation and thus true prevalence of patients able to maintain remission off therapy can not be inferred .
a french observational study confirms that romiplostim can be successfully discontinued : of the 28/54 responding patients , 8 remained in complete remission off therapy at a median follow up of 13,5 months ( range 5 - 27 )
. data from a recently presented interim analysis of a phase 2 study of platelet response and remission rates in itp patients receiving romiplostim show that 11 of 38 evaluable patients ( 29% ) were able to maintain remission ( i.e. 24 weeks of platelet counts 5010/l ) off any treatment .
we report our experience with the peptibody romiplostim in a small series of patients unresponsive to immunosuppressive therapy who were treated with this tpo - ra for variable lengths of time . some of these patients were able to discontinue therapy after achieving response , without relapsing at long - term follow - up .
between september 2009 and may 2014 a total of 30 patients ( 11 m ; mean age at romiplostim treatment 50.7 yrs , range 18 - 82 ) received romiplostim at two collaborating centers . patients with shorter follow - up on treatment with romiplostim or on eltrombopag are not included in the present analysis .
patients were defined either as non responders or refractory according to the international working party ( iwp ) proposed standardization of terminology for itp .
all patients are enrolled in a local italian registry ( rel - itp registry ) , and informed consent to demographic and clinical data use is given at enrollment .
the rel registry has received approval by the human subjects research review board of both participating hospitals .
of the 27 responders : 1 patient ( # 4 ) was lost to follow - up ; 1 patient ( # 5 ) discontinued romiplostim due to acute myocardial infarction , at the time of sae , romiplostim dose was 10 g / kg / week and platelet counts were 8410/l ; in 5/27 patients ( # 6 - 10 ) romiplostim was used as bridge to splenectomy ; 5/27 patients ( # 11 - 15 ) lost response at 11 , 6 , 11 , 12 and 11 months respectively ; neutralizing anti - romiplostim antibodies could be searched for in 3/5 patients ; in three ( # 13 , 14 and 15 ) the test yielded a positive result ; the remaining two patients could not be tested ; in 2/27 patients ( # 16 and 17 ) romiplostim administration is ongoing ( 56 and 12 months respectively ) ; 13/27 patients ( # 18 - 30 ) achieved stable , safe platelet counts and were able to stop romiplostim after a mean of 43.3 weeks ( range 12 - 122 ) on therapy with sustained response maintained at a mean of 28.8 months ( range 15 - 55 ) .
strict platelet monitoring was maintained during follow up off therapy . in 7/13 patients a decreased platelet count compared to a previous control was found weeks from discontinuation of weekly romiplostim administration .
these patients were re - exposed to a limited number of one shot low ( 1 or 2 mcg / kg ) dose of romiplostim and regained a stable response , as shown for four patients in figure 1 .
patient # 29 developed lower limb superficial phlebitis while on romiplostim 1 g / kg on alternate weeks and warfarin was started ; platelets were 13510/l at the time of the event ; screening for lupus anticoagulant , anti - phospholipids antibodies , anti - beta2glycoprotein1 was negative .
three patients ( # 18,20,28 ) had received the last rituximab course 4 , 6 and 33 weeks before starting romiplostim ; one patient ( # 19 ) received a first course of romiplostim as bridge to splenectomy having failed steroids and cyclosporine ; a week after surgery he relapsed with severe thrombocytopenia and was re - treated with romiplostim .
he received a total of 7 romiplostim doses administered over a 22 week period of time ; romiplostim was discontinued at 22 weeks from splenectomy since stable , 100109/l platelet counts were achieved .
bone marrow biopsies for detection of fibrous changes during romiplostim use were not performed since most of our patients received treatment for less than 18 months .
overall , our experience with romiplostim in real life practice is in line with reported findings from controlled studies with 90% of patients ( 27/30 ) responding .
however , in our experience the percentage of patients able to discontinue romiplostim without relapsing is noteworthy : 48% , if we consider the whole number of romiplostim responders ( 13 of 27 responders ) and 65% if we consider only patients who received long - term treatment ( 13 of 20 patients ) i.e. not considering patients receiving romiplostim as bridge to splenectomy , lost to follow - up , or who discontinued the drug because of sae . in 5 chronic itp patients out of 13 long term responders , romiplostim seemed to be the only treatment responsible for sustained response .
indeed , it has been proposed that tpo - ra therapy may result in improved immune regulation by regulatory t cells ( tregs ) possibly restoring immune tolerance.14 similar immune - modulating effects have also been described for other treatment modalities ( e.g. rituximab , high - dose dexamethasone , intravenous immunoglobulin ) which result in sustained responses in a fraction of itp patients.15,16 in the remaining 8 patients , response might have been either spontaneous ( 2 newly diagnosed and 3 persistent disease patients ) or secondary to rituximab ( 2 patients ) or splenectomy ( 1 patient ) .
nevertheless , use of romiplostim may be a treatment option for patients with persistently low platelet counts awaiting for platelet recovery , either it be spontaneous or secondary to disease - modifying treatments for which a possible late - response can be anticipated .
no specific patient s features ( e.g. age , itp duration , lines of previous treatment ) nor pattern of early response ( e.g. dose requirements , time to response ) seemed to consistently predict for sustained response off therapy .
however , it seems that patients achieving safe platelet counts at lower dosages are probably worth a try of therapy tapering and discontinuation .
manufacturer dose adjustment rules allow romiplostim to be discontinued when appropriate and clinical judgment was used to manage patients .
this has been specifically tested and demonstrated for eltrombopag and it is conceivable also for romiplostim : one of the patients presented by newland received a single romiplostim dose after 11 weeks off therapy and regained high platelet counts ; thereafter , hemostatic platelet counts were maintained without any therapy for 2 years .
all 7 patients who were reexposed to romiplostim weeks after weekly administration was stopped ( table 2 and figure 1 ) , regained a platelet response .
knowledge that tpo - ra can be safely administered on a on - demand basis without loss of effectiveness offers the possibility of re - exposing relapsed patients without the threat of these patients not being able to regain a response . moreover , need of on demand therapy does nt seem to predict for lost of long - term response to romiplostim .
this new finding is probably worth being taken into account in planning prospective studies of feasibility of romiplostim discontinuation .
the finding that at least 3 of 5 patients who abruptly lost response to romiplostim tested positive for neutralizing antibodies suggests that development of these antibodies may be a more frequent event than expected .
being a retrospective observational study , our results should be interpreted with caution , but still they suggest that in a significant fraction of patients , in real world practice , sustained remission without disease recurrence may be obtained after a relatively short - term administration of romiplostim .
to date , because of their known mechanism of action , tpo - ra are thought to be effective only while the treatment is ongoing and the proper dose is being administered .
our observations support the proposal of using romiplostim as bridge to recovery , either it be spontaneous ( e.g. in newly diagnosed or persistent itp ) , tpo - ra induced or representing a late - response to previously administered treatments , rather than long - term treatment .
first of all , concern about tpo - ra long - term sides effects ( marrow fibrosis , increased risk of thrombotic events ) , especially in younger patients , would be greatly reduced . moreover , treatment costs , which currently also limit their use would be less of an issue .
if results on persistent remissions after short - term romiplostim use were to be confirmed in larger patient population , this approach could be used to defer or avoid splenectomy and to spare patients the untoward effects of prolonged immunosuppressive treatments .
this would be especially beneficial in newly diagnosed severe itp failing first line therapy with steroids .
future biological and intervention studies are needed in order to identify predictive factors of long term sustained response , allowing clinicians to tailor the best treatment for each itp patient .
thrombopoietin mimetics are new treatment options for patients with immune throm - bocytopenia ( itp ) . because of their mechanism of action 
 , long - term administration was envisioned in order to maintain effective thrombopoiesis . 
 we report on 30 romiplostim treated patients : 13/27 responders ( 48% ) achieved stable platelet counts on a mean romiplostim dose of 2.43 g / kg and were able to stop romiplostim after a mean of 44.3 weeks ( range 12 - 122 ) on therapy with sustained response maintained at a mean of 26 months ( range 12 - 52 ) . 
 no bleeding events occurred during the observational period . 
 no specific patient s features nor pattern of early response seemed to predict for sustained response . 
 however , patients achieving safe platelet counts at lower dosages are probably worth a try of therapy tapering and discontinuation . 
 our observations support feasibility of romiplostim safe suspension in a relevant proportion of itp patients .