Interferon gamma (IFNγ)-targeted immunotherapy with emapalumab, a fully human monoclonal
antibody, was recently approved by the US Food and Drug Administration for the treatment
of adult and pediatric patients with primary hemophagocytic lymphohistiocytosis (HLH)
who have refractory, recurrent or progressive disease or intolerance with conventional
HLH therapy.
1,2
Moreover, emapalumab has shown promising efficacy in the treatment of patients with
graft failure (GF) requiring a second allogeneic hematopoietic stem cell transplantation
(HSCT).
3
Interestingly, there is growing evidence to support common pathophysiolological mechanisms
between HLH and immune-mediated GF, highlighting the key role of IFNγ in both conditions.
3
IFNγ is a cytokine produced by macrophages and lymphocytes that plays a critical role
in both innate and adaptive immune responses. In patients with complete IFNγ receptor
deficiency or developing anti-IFNγ autoantibodies, the absence of IFNγ biological
activity leads to an increased susceptibility to specific infections, such as mycobacterial
infections.
4,5
For this reason, latent tubercolosis (TB) infection represented an exclusion criterion
in clinical trials investigating the therapeutic role of emapalumab in primary (clinicaltrials.gov
identifiers: NCT03312751; NCT01818492) and secondary (clinicaltrials. gov identifiers:
NCT03311854) HLH.
Here we report a case of secondary HLH-related GF in the context of HLA-haploidentical
HSCT treated with emapalumab in the presence of concomitant life-threatening infections
including disseminated bacille Calmette- Guérin disease (BCGitis).
Table 1.
Characteristics of the three HLA-haploidentical (haplo)-hematopoietic stem cell transplantations
performed.
Figure 1.
Clinical, brain magnetic resonance imaging (MRI) and chest computed tomography (CT)
images of tubercolosis (TB) and fungal infections, and schematic summary of treatments.
(A) Localized abscesses on lower limbs at the sites of polyethylene glycol-modified
adenosine deaminase injection before surgical incision. (B) Localized abscesses on
lower limbs at day +100 after the third haplo-HSCT. Surgical incision was performed
before HSC-gene therapy (GT). (C) Brain MRI at diagnosis of intracerebral TB granuloma.
Sagittal and coronal post-contrast T1W brain MRI images show a hypothalamic contrast
enhancing lesion suggestive for tuberculous granuloma. (D) Brain MRI at day +100 after
the third haplo-HSCT showing marked reduction of the tuberculous granuloma. (E) CT
images of the lungs at time of aspergillosis diagnosis after the second haplo-HSCT.
Axial chest CT images with lung window (left) and mediastinal window (right) show
a left lower lobe pulmonary mass compatible with pulmonary aspergillosis. (F) CT images
of the lungs at day +100 after the third haplo-HSCT showing marked improvement. (G)
Schematic representation of the treatment given before and during the third haplo-HSCT
to control secondary HLH and prevent graft failure. MPD: methylprednisolone; VP-16:
etoposide; CTX: cyclophosphamide; ATG: anti-thymocyte globulin; Cs-A: cyclosporine-A.
The patient is a 4-year old girl with severe combined immunodeficiency caused by adenosine
deaminase deficiency (ADA-SCID) referred to our institution for ex vivo hematopoietic
stem cell (HSC)-gene therapy (GT) with Strimvelis® in the absence of a human leukocyte
antigen (HLA)-identical sibling donor.
6
She was in poor clinical condition at presentation with bilateral abscesses on lower
limbs, corresponding to the sites of polyethylene glycol-modified adenosine deaminase
(PEG-ADA) injections (Figure 1A). Presence of Mycobacterium bovis was identified by
direct next-generation sequencing performed on the material drained from the limb
abscesses using the Deeplex®Myc-TB, an all-in-one test for specieslevel identification,
genotyping and prediction of antibiotic resistance in Mycobacterium tuberculosis complex.
Results were further confirmed by standard mycobacteriology procedure and whole genome
sequencing of the strain. Moreover, magnetic resonance imaging (MRI) documented an
intracerebral granuloma (Figure 1C) and vertebral osteolytic lesions, that, along
with the limb abscesses, led to the diagnosis of disseminated BCGitis, as reactivation
of the BCG vaccine strain received at birth. She was treated with surgical incision
of the abscesses and anti-TB treatment (four-drug regimen [isoniazid, rifampicin,
ethambutol, moxifloxacin] for 12 months as intensive phase; two-drug regimen [isoniazid,
rifampicin] for 6 months as continuation phase). After 7 months of anti-TB treatment,
at resolution of cutaneous abscesses and with residual encephalic mycobacterial lesions,
the patient was considered eligible and treated with Strimvelis®. Failure of engraftment
of gene-corrected HSC was declared at day +90 and enzyme replacement therapy (ERT)
was resumed.
Subsequently, due to the lack of a matched unrelated donor and after ERT withdrawal,
the patient received a first HLA-haploidentical HSCT after αβ+ T-cell and CD19+ B-cell
depletion (TCD) from the father after reduced toxicity conditioning regimen (Table
1).
7
However, HSCT failed due to primary GF, likely related to concomitant adenovirus reactivation
in the periengraftment phase. A second paternal haplo-HSCT was performed after reduced
intensity conditioning employing exceeding HSC cryopreserved from the first transplant
and infused on d+31 post first HSCT (Table 1).
On day +13 after the second haplo-HSCT, the patient showed persistent fever, hepatosplenomegaly,
high levels of triglycerides (383 mg/dL) and markedly elevated inflammatory markers
such as ferritin (18,000 mg/dL) and soluble IL2 receptor (16,809 pg/mL; reference
values 600-2,000) (Figure 2A and B). Donor chimerism on both peripheral blood (PB)
and bone marrow (BM) was documented on days +10 and +13, respectively; however, it
was followed by secondary GF with complete loss of donor engraftment (day +18). BM
morphology showed hypocellularity with features of active hemophagocytosis. A secondary
HLH was diagnosed based on 6 out of 8 HLH-2004 criteria,
8
likely triggered by concurrent infections, including Stenotrophomonas maltophilia
bacteremia, invasive pulmonary aspergillosis (Figure 1E) and adenovirus reactivation.
Treatment with methylprednisolone (2 mg/kg/day) and high-dose immunoglobulins was
started.
In order to control HLH and reduce the possibility of GF after a third HSCT, compassionate
use of emapalumab was requested and approved for this severely immunocompromised patient
unable to tolerate standard HLH immunochemotherapy.
At time of emapalumab initiation, adenovirus reactivation and invasive pulmonary aspergillosis
were active: adenovirus was detected both in plasma and stool with 1,940 copies/mL
and >1,000,000 copies/mL, respectively; while galactomannan levels were above the
upper limit of detection (index >6). Intensive antimicrobial treatment included antivirals
(intravenous cidofovir, later switched to oral brincidofovir) and antifungals (voriconazole
plus anidulafungin, later switched to liposomial amphotericine- B plus anidulafungin
to minimize drugs interactions). Conversely, rifampicin and isoniazid were continued
as secondary prophylaxis to avoid the risk of reactivation of TB, which was regularly
monitored through blood cultures, fecal polymerase chain reaction (PCR) for Mycobacterium
bovis and brain MRI. Emapalumab was administered intravenously twice a week for a
total of 15 infusions with the objective of prompt tapering of glucocorticoids. After
the first dose at 1 mg/kg, emapalumab dose was increased to 3 mg/kg: the laboratory
parameters, while not worsening, did not show any satisfactory improvement. Thereafter,
emapalumab dose was increased to 6 mg/kg, based on deterioration of inflammatory parameters
(e.g., ferritin, C-reactive protein) (Figure 2A). IFNγ levels were not particularly
elevated in this patient, as documented by CXCL9 values around 260 pg/mL at start
of emapalumab treatment (Figure 2B). Nonetheless, the pharmacokinetics (PK) of emapalumab
(Figure 2C) was affected by target-mediated drug disposition, documenting high IFNγ
production and requiring emapalumab dose increase. CXCL9 progressively decreased to
levels below 80 pg/mL, documenting complete neutralization of IFNγ. By the time of
the third haplo-HSCT, glucocorticoids dose was reduced to approximately 50% of the
starting dose, while maintaining a good clinical control of HLH. The patient, despite
the occasional temporary worsening of a few HLH laboratory parameters, did not progress
into overt HLH, likely due to the neutralization of IFNγ.
The patient received the third TCD haplo-HSCT from the mother after a total of six
emapalumab doses. Conditioning regimen included chemotherapeutic agents active against
HLH,
8
while cyclosporine-A (Cs-A) was added for graft-rejection prevention (Table 1). Anti-HLA
antibodies were undetectable before and after HSCT. Neutrophil and platelet engraftment
occurred on days +10 and +14, respectively. BM aspirate at day +21 was normo-cellulated
with no evidence of hemophagocytosis and showed full donor chimerism. Emapalumab was
administered until achievement of sustained donor engraftment (day +28) (Figure 1G).
No adverse events occurred. HLH clinical and laboratory parameters progressively improved
(Figure 2A and B) allowing Cs-A and steroids tapering and ultimately discontinuation
(days +36 and +59, respectively) (Figure 1G).
Remarkably, during blockade of IFN-γ with emapalumab, infections remained stable or
improved with antimicrobial medications. At the end of treatment, no sign of reactivation
of cutaneous TB lesions was observed (Figure 1B) and the brain imaging showed improvement
of the lesions documented prior to emapalumab (Figure 1D). Bacteremia resolved and
invasive pulmonary Aspergillosis improved with favorable radiological evolution (Figure
1F) and reduction of galactomannan up to negativity at day +132 post HSCT. After 8-week
treatment with emapalumab, at day +39 post HSCT, adenovirus became undetectable in
plasma. Treatment with brincidofovir was continued until negativity also in stool
and therefore withdrawn one month later. At day +100 post HSCT the patient was clinically
well with full donor chimerism on total BM and PB, as well as on lymphoid and myeloid
subpopulations (Table 1). She is currently nine months after the third haplo HSCT
and the patient remains in good clinical conditions and is infection-free. Based on
emapalumab half-life, the patient has remained on anti-TB prophylaxis to mitigate
the risk of reactivation until measurable levels of the drug were present.
Figure 2.
Significant inflammatory markers from the hemophagocytic lymphohistiocytosis (HLH)
diagnosis up to the end of treatment with emapalumab and pharmacokinetics (PK) of
the drug. (A) Serum ferritin (normal values [nv]: 15-150 ng/mL) and C-reactive protein
(CRP) (nv <6 mg/L); trends are reported in red and blue lines, respectively. (B) IL2
receptor (nv 600-2000 pg/mL) and CXCL9 levels are reported in purple and green, respectively.
Normal ranges are reported in light yellow. (C) Concentration-time profile of emapalumab
in the patient. Green dots and solid lines represent observed emapalumab concentrations.
Black solid lines represent simulated concentrations for the specific patient (i.e.,
taking into consideration the dosage schedule and measured total interferon gamma
(IFNγ) concentrations) based on the population pharmacokinetic model of emapalumab
in HLH patients. Gray area surrounded by orange dotted lines represents the 90% prediction
interval of the simulated concentrations. Dotted red line represents the limit of
quantification of the bioanalytical assay (62.5 ng/mL). Ticks and numbers on the top
line represent times of administration and dose in mg/kg. IL2: interleukin 2; CXCL9:
chemokine (C-X-C motif) ligand 9; HSCT: hematopoietic stem cell transplantation.
In conclusion, we report the case of a very fragile, heavily immunosuppressed patient
affected by ADASCID who experienced GF after multiple HSCT in the presence of life-threatening
infections including disseminated TB, who was safely treated with emapalumab.
The activation of the IFNγ pathway has a well-documented double role both in controlling
mycobacterial infections and, also, in sustaining HLH hyperinflammatory response.
10,11
In our patient, we had to face both challenges: on the one hand to prevent TB reactivation
and on the other to inhibit the hyperinflammation responsible for both HLH and GF.
Upon review of emapalumab safety and efficacy data reported in primary
2,12,13
and secondary
14
HLH, and despite the potential risk of TB reactivation, the benefit/risk ratio of
treating with emapalumab was deemed favorable. Interestingly, during emapalumab treatment,
the initial TB abscesses remained inactive and brain TB findings improved. In this
context, neutralization of IFNγ might have contributed to control HLH without the
prolonged use of additional myelosuppressive drugs. Moreover, since a third GF was
not observed, our findings suggest that, in association with other lines of immunosuppressive/chemotherapic
agents, emapalumab might have played a role in reducing the risk of graft rejection,
as already shown in both murine models and humans.
3,15,16
In addition, while an intrinsic defect of the mesenchymal/osteblast compartment in
ADA-SCID patients with reduced capacity to support in vitro and in vivo hematopoiesis
9
may have contributed to the repeated GF, the concomitant use of Cs-A in the peri-transplant
phase and the mega-dose of CD34+ cells infused after the third haplo-HSCT may have
played a role in preventing rejection.
This seminal case suggests the feasibility and safety of emapalumab administration
to manage secondary HLH and repeated GF also in patients bearing multiple active infections,
including TB.
Supplementary Material
Disclosures and Contributions