Abstract
Antitumor activity of nab-sirolimus versus mTOR inhibitors temsirolimus, sirolimus, and everolimus in A549 NSCLC xenografts.
Author
person
Shihe Hou
Aadi Bioscience, Pacific Palisades, CA
info_outline
Shihe Hou, Maria Zalath, Andrew Kwon, Edward Spindler
Full text
Authors
person
Shihe Hou
Aadi Bioscience, Pacific Palisades, CA
info_outline
Shihe Hou, Maria Zalath, Andrew Kwon, Edward Spindler
Organizations
Aadi Bioscience, Pacific Palisades, CA
Abstract Disclosures
Research Funding
No funding sources reported
Background:
The mTORC1 pathway, often activated by mutations in genes like
TSC1, TSC2, PIK3CA, PTEN, STK11,
and
KEAP1
, plays a pivotal role in cancer progression; in some settings, alterations in
STK11
and
KEAP1
may be associated with treatment resistance and poor prognosis. Despite the broad importance of the mTORC1 pathway in cancer cell growth and survival, mTOR inhibitors (mTORis) temsirolimus (TEM), sirolimus (SIRO), and everolimus (EVE) have limited clinical application in the cancer setting.
nab
-Sirolimus, an injectable form of albumin-bound SIRO that leverages unique transport properties of albumin known to increase tumor drug accumulation, is approved for treatment of malignant PEComa. Here, we report the antitumor activity of
nab-
sirolimus
in comparison to other mTORis in A549 NSCLC (
KRAS
G12S,
STK11
Q37*, and
KEAP1
G333C) xenografts, and the correlation of antitumor activity, tumor PK profile, and mTOR pathway suppression.
Methods:
Athymic mice bearing subcutaneous A549 NSCLC xenografts were treated with either saline or equal weekly doses of
nab-
sirolimus (administered intravenously [IV]; 5 or 15 mg/kg/week), TEM (IV; 5 mg/kg/week), or SIRO or EVE (both oral; 15 mg/kg/week). Tumors were harvested at different time points after mTORi treatment and analyzed for tumor drug levels (LC-MS/MS) and mTOR pathway biomarkers (pS6 and p4EBP1) via western blot (WB).
Results:
In A549 xenografts,
nab-
sirolimus (IV) treatment resulted in significantly greater suppression of tumor growth compared with TEM (IV), SIRO (oral), and EVE (oral) (Table). Average intratumoral drug concentrations 24 hours after IV mTORi treatment were significantly higher with
nab-
sirolimus (420-539 ng/g) compared with TEM (TEM [parent] 34.9 ng/g; SIRO [active metabolite measured from TEM] 13.2 ng/g) and compared with 7-day steady-state concentrations for oral SIRO (17 ng/g) and EVE (10 ng/g). WB confirmed that
nab-
sirolimus consistently inhibited mTOR targets pS6 and p4EBP1, whereas TEM, SIRO, and EVE were less effective.
Conclusions:
nab
-Sirolimus resulted in significantly higher intratumoral drug concentration, stronger inhibition of mTOR targets, and greater antitumor activity compared to other IV and oral mTORis in a
KRAS/STK11/KEAP1
mutated NSCLC xenograft model. These results support further clinical evaluation of
nab
-sirolimus as a single agent or in combination with other therapeutic agents in oncology.
Dosing and antitumor activity of
nab-
Sirolimus vs TEM, SIRO, and EVE.
Treatment
N
Weekly dose (mg/kg/wk)
Schedule, Route
Day vs Saline
TGI vs saline (%)
Tumor Growth vs
nab-
Sirolimus (ANOVA),
P
-value
nab-
Sirolimus
8
5
2.5 mg/kg, 2x/wk, IV
35
78.3
-
TEM
8
5
2.5 mg/kg, 2x/wk, IV
35
45.0
0.01
nab-
Sirolimus
8
15
7.5 mg/kg, 2x/wk, IV
35
94.2
-
SIRO
8
15
2.14 mg/kg, daily, oral
35
30.0
0.0007
nab-
Sirolimus
10
15
7.5 mg/kg, 2x/wk, IV
29
95.4
-
EVE
10
15
2.14 mg/kg, daily, oral
29
68.3
0.07
Clinical status
Pre-clinical
1 organization
4 drugs
1 target
Drug
nab-sirolimusDrug
temsirolimusDrug
sirolimusDrug
everolimusTarget
mTORC1Organization
Aadi Bioscience