1.1 Adrenal pheochromocytoma/paraganglioma pheochromocytoma (PCC) and Paraganglioma (PGL)
(pheochromocytoma and paraganglioma (PPGL) are rare malignant tumors with neuroendocrine
function and metastatic potential. The incidence is 0.4-2.1 persons/million, 80%-85%
originate from the adrenal medulla, and 15%-20% originate from the neural crest tissue from
the neck to the pelvis. The PPGL metastasis rate at initial diagnosis is 10%, and the risk of
metastasis is as high as 34-69% for those with SDHB gene mutations. The recurrence rate of
PPGL patients after radical resection was 30%, 47% recurred with multiple nodules, 58% with
metastasis. The most common sites of metastasis were lymph nodes and bone (70-80%), followed
by lung and liver (50%). In addition, some PPGL is difficult/unresectable due to its
proximity to important structures such as large blood vessels or nerves, and the 5-year
survival rate for advanced PPGL is 30%-60%.
Early PPGL can be cured by surgery, but late PPGL is mainly systemic therapy, such as
chemotherapy, targeted drugs and nuclide therapy. The main chemotherapy regimen for advanced
PPGL is cyclophosphamide
- - vincristine - dacarbazine (CVD regimen), and ESMO guidelines
recommend CVD for patients with rapid tumor progression and heavy tumor burden.
The objective
response rate of CVD regimen was 33%, the median duration of response was 1.3 years, and the
5-year survival rate of patients with effective CVD was 51%. The main limitations of CVD in
the treatment of advanced PPGL are
- (1) The average number of cycles required for CVD
chemotherapy is 11.6±10.8 months; (2) The incidence of CVD related toxicity, such as bone
marrow suppression and neurotoxicity, was 50%.
Some patients could not maintain treatment due
to intolerance, and long-term use of the above drugs could increase the incidence of
hematological tumors, which may be related to the alkylating properties of daparbazine.
Domestic guidelines and the FDA recommend 131I-MIBG for the treatment of advanced PPGL. Loh
et al. reviewed and analyzed 21 central LSA-131I-MIBG clinical studies: 30% patients could
have Partial Response (PR); Gonias S et al. Phase II clinical study of HSA-131I-MIBG in the
treatment of advanced PPGL: 22% of patients could have PR. Two 131I-MIBGs show good efficacy,
but there are no phase III clinical studies to further validate efficacy and safety.
Limitations of radionuclide therapy lie in
- (1) the narrow range of indications: (1) ESMO
guidelines indicate that only 50% of patients with positive MIBG scan are suitable.
②
Pregnant women and pregnant patients should not use;
- (2) Severe hematological toxicity: the
incidence of myosuppression was 4%-79%, about 40% of patients treated with low-dose 131I-MIBG
had grade 3/4 toxicity, while those treated with high-dose 131I-MIBG had up to 80%, of which
25% needed hematological therapy and secondary hematological tumors could be developed .
In addition, at present, the units that can carry out nuclide therapy in China
are limited, and patients can not perform nuclide therapy again after receiving progress of
nuclide therapy.
1.2 Tyrosine kinase inhibitors (TKI) and advanced adrenal pheochromocytoma/paraganglioma
Tyrosine kinase (TK) is a key site in the activation and regulation of cell proliferation
signaling pathways. Abnormal TK pathway caused by mutation, translocation or amplification
can lead to tumor occurrence, progression, invasion and metastasis. Tyrosine kinase
inhibitors (TKI) mainly act on vascular endothelial growth factor receptor (VEGFR), platelet
growth factor (PDGFR) and insulin family receptor (InsR). TKI acts on advanced PPGL through
the pseudo-hypoxia pathway and VEGF angiogenesis pathway.
Advanced PPGL with abundant blood supply and high expression of angiogenic factor (VEGF) can
promote tumor neovascularization and provide oxygen and nutrition for tumors. TKI has a good
therapeutic effect on advanced PPGL with high VEGF expression, which may be related to its
blocking of VEGF signaling pathway, continuous inhibition of tumor neovascugenesis and
promotion of abnormal blood vessel normalization. In addition, HIF axis misalignment can also
promote the development and transfer of PPGL. SDH gene mutations are the most common in PPGL
(including SDHA, SDHB, SDHC, SDHD), which cause abnormalities in the subunit encoding the
succinate dehydrogenase complex (SDH) and block the tricarboxylic acid cycle (TCA). Abnormal
TCA can inhibit hypoxia-inducing factor (HIF-α) proline hydroxylase, and HIF-α accumulation
will activate the pseudo-hypoxia pathway and up-regulate the expression of VEGF and other
factors.
ESMO guidelines recommend sunitinib for the treatment of advanced PPGL. Currently, the only
prospective phase II clinical study showed that 3 cases (13%) had PR (SDHB, SDHD, RET gene
mutations, respectively). A retrospective study of 17 cases of advanced PPGL treated by MD
Anderson and Gustavvy-Roussy et al. showed that there were 3 cases of PR and 5 cases of SD (6
of which were SDHB or VHL gene mutations). In the study , grade 1-2 toxicity was the most
common, with about 68% of patients presenting symptoms such as fatigue, nausea and vomiting,
palm-plantar dyspepsia, etc., while only 56%/12% of patients presented 3/4 toxicity, mainly
manifested as nausea, vomiting and hypertension, without hematological toxicity.
Retrospective studies have also shown that Renvastinib, pazopanib, acitinib and other TKI
have certain efficacy in advanced PPGL, but there is a lack of prospective clinical evidence.
Hassan Nelson L et al. treated 11 cases of advanced PPGL with lenvatinib, and the results
were 5 cases PR, 3 cases SD, and the median PFS was 14.7 months. Mauricio Emmanuel Burotto
Pichun et al. are conducting a study on the treatment of 11 cases of advanced PPGL with
acitinib: 4 cases of PR and 6 cases of SD. The above studies show the preliminary efficacy of
various TKI, and the effect may be better for SDHB mutations, with a controllable safety,
mainly hypertension. In 2017, preliminary results of a prospective clinical study of
cabotinib in the treatment of advanced PPGL were reported in the conference abstract: ORR of
45%, PFS of 11 months, and no grade 3/4 toxicity. In summary, TKI monotherapy in the
treatment of advanced PPGL shows some effect, but it is still not satisfactory.
There is currently no standard first-line treatment for advanced PPGL. NCCN guidelines and
China's expert consensus (2020 edition) recommend the use of tumor reduction surgery
(palliative resection) combined with radiotherapy, radionuclide therapy or systemic
chemotherapy and other treatment options, but the above methods have uncertain efficacy and
certain limitations, still need to be confirmed by prospective experiments, so patients are
recommended to participate in clinical trials.
1.3 Application of antirotinib hydrochloride in advanced adrenal
pheochromocytoma/paraganglioma Allotinib (AL3818) is manufactured by Zhengda Tianqing
Pharmaceutical Group Co., LTD. (CTTQ; Lianyungang, Jiangsu, China) self-developed TKI drugs,
targeting VEGFR1-3, FGFR1-4, PDGFRα, G, β, rearrangement (RET) and stem cell factor receptor
(c-Kit) during transfection [26]; Anlotinib has shown good anticancer activity in vitro/in
vitro [27]. A multicentre, randomized, controlled Phase II clinical study of anlotinib in
first-line treatment of metastatic renal cell carcinoma (mRCC) (NCT02072031)[28] showed
similar efficacy of anlotinib and Sunitinib: There were no significant differences in median
PFS (17.May vs.#46; 16.June, P > 0.05), OS, ORR and DCR (P > 0.05), but the toxicity of anrotinib
was lower, and the incidence of ≥3/4 toxicity was significantly lower than that of Sunitinib
(28.9% vs.#46;55.8%, P < 0.01). The main symptoms were hypertension and hand-foot syndrome, and
no hematological toxicity was found. In addition, Lin J et al. also confirmed that anlotinib
and Sunitinib had similar efficacy but higher safety. TKI treatment of advanced PPGL has a
similar mechanism of action, but anlotinib safety may be better. In addition, our team has a
certain foundation in the study of anrotinib in the treatment of advanced PPGL. In the early
stage, anrotinib monotherapy was used to treat advanced PPGL in 4 cases and PR in 2 cases (1
case was a SHDB mutation), and the adverse reactions were mostly grade 1-2, with hypertension
and hand-foot syndrome as the main manifestations. Therefore, antirotinib may have better
efficacy and safety in advanced PPGL, which is worthy of further clinical exploration.
1.4 Application of peamprizumab in advanced adrenal pheochromocytoma/paraganglioma PD-1/PD-L1
monoclonal antibody kills tumors by activating its own normal anti-tumor immune mechanism. In
2014, Pembrolizumab achieved results in melanoma, officially ushering in the era of global
immunotherapy. Subsequently, indications and significant curative effects were also obtained
in multi-tumor species such as non-small cell lung cancer, gastric cancer and kidney cancer.
PD-L1 is mainly expressed in tumor cells and antigen-presenting cells (APCs), and is closely
related to tumor immune escape [33] : PD-L1 receptor of tumor cell membrane binds to PD-1
receptor of T cell membrane, which weakens the ability of cytotoxic T lymphocytes to kill
tumor cells. PD-1/PD-L1 mab blocks the above signaling process and restores/activates the
anti-tumor activity of T cells.
A study in Peking Union Medical College Hospital [35] showed that 59.7% were positive for
PPGL PD-L1 expression (HIS>10), and the positive rate of PD-L1 in advanced PPGL was
100%(1/1). Study [36] showed that PD-L1 expression was positive in 4 out of 10 advanced PPGL
cases (40%). Studies indicated that the cytotoxic T lymphocyte infiltration level was
increased in advanced PPGL (P=0.092). Therefore, PD-1 monoclonal antibody may have some
significance in the treatment of advanced PPGL. At present, only A few cases have been
reported in the treatment of advanced PPGL with PD-1 monoclonal antibody. The Phase II
clinical study conducted by Naing A et al. in the treatment of advanced PPGL patients with
pembrolizumab showed that 43% (4 cases) had no progress at 27 weeks (6.75 months). This
suggests that PD-1 monoclonal antibody has a certain effect in the treatment of advanced
PPGL, but PD-1 monotherapy can not meet the clinical needs.
KATO Y et al. proposed that the effective rate of PD-1 monoclonal antibody in the single
treatment of solid tumors was 20%-30%, and the therapeutic effect was not satisfactory. The
study of PD-1 monoclonal antibody combined with TKI in the treatment of liver cancer suggests
that the combination of PD-1 monoclonal antibody can reverse the immunosuppressor tumor
microenvironment in which PD-1 monoclonal antibody is ineffective, and assist PD-1/PD-L1
monoclonal antibody to activate cytotoxic T lymphocytes. The efficacy of acitinib combined
with PD-1 mab in the second-line treatment of patients with metastatic renal cancer was
significantly higher than that of acitinib (ORR: 33.6% vs.#46; 20.1%, P=0.015) (PFS: 11.7 months
vs.#46; 7.5 months, P=0.002).
Piamprilizumab (Anicol) is a new PD-1 monoclonal antibody developed by Zhengda Tianqing
Pharmaceutical Group Co., LTD., which has been approved for Hodgkin's lymphoma (R/R cHL) and
squamous non-small cell lung cancer (NSCLC) indications in China. Pembrolizumab has achieved
significant efficacy in the treatment of classic Hodgkin lymphoma, metastatic nasopharyngeal
carcinoma, gastric/esophageal junction adenocarcinoma and other tumor species in clinical
studies, with ORR of 89.4%, 29.7% and 26.3%, respectively .
Anicol is a humanized IgG1 subtype of PD-1 monoclonal antibody that eliminates Fc effects.
The IgG1 subtype reduces immune escape by eliminating antibody-dependent cell-mediated
cytotoxicity (ADCC), antibody-dependent cell-mediated phagocytosis (ADCP), and
complement-dependent cytotoxicity (CDC). The combination of anil with FcR can reduce the
occurrence of adverse immune reactions , and the incidence of grade 3 and above toxicities
such as immune-associated pneumonia, hepatitis, myocardium, and pancreatitis is lower than
that of sindillizumab, tirellizumab, and triplizumab. Therefore, this study intends to use
anicol combined with anlotinib to explore its efficacy and safety in advanced PPGL.
1.5 Application of antirotinib combined with PD-1 monoclonal antibody in advanced
pheochromocytoma/paraganglioma The combination of TKI and PD-1 monoclonal antibody is a
research hotspot in the treatment of advanced tumors. Target-free therapy has been widely
used in renal, urothelial, lung, liver and other tumors, and has achieved remarkable efficacy
[46].
Only a few cases of combined treatment for advanced PPGL have been reported at home and
abroad. In Taizhou Hospital of Zhejiang Province in 2022, a patient was treated with
palizumab injection 200 mg(once every 3 weeks) for intravenous immunotherapy, combined with
anrotinib 10 mg orally (once a day, 14 days and 7 days, every 3 weeks for a course of
treatment). The left adrenal mass (9.6cm →8.4cm) and the multiple intrahepatic mass (up to
9.3cm →8.8cm) were both reduced. In the early stage, our team used anrotinib combined with
PD-1 monoclonal antibody to treat 3 patients, and the efficacy reached PR 66% (2/3),
including 1 case with SHDB mutation. This suggests that targeted immunotherapy for advanced
PPGL may have better efficacy.
In an open, multicenter, phase Ib/II clinical study of anlotinib combined with piamprizumab
in the treatment of advanced hepatocellular carcinoma, the ORR was 31% and the DCR was 82.8%.
The median PFS was 8.8 months (95% CI 4.0-12.3 months). 80% were grade 1/2 toxicity, such as
elevated AST, elevated ALT, elevated blood bilirubin, etc. Only 19.4% had grade 3/4 toxicity
such as hypertension and rash. This is an improvement in efficacy and a decrease in toxicity
compared to the treatment of advanced hepatocellular carcinoma with altilizumab combined with
bevacizumab or carrilizumab combined with apatinib.
At present, there have been no studies on the combination of targeted drugs and immunodrugs
in the treatment of advanced PPGL at home and abroad. Therefore, this study will for the
first time apply the combination of TKI drugs (antirotinib) and PD-1 monoclonal antibody
(Pembrolizumab) to metastatic/unresectable pheochromocytoma/paraganglioma, so as to explore
the efficacy and safety of combined drugs in the treatment of advanced
pheochromocytoma/paraganglioma.