diff -ruN a/src/pdm/backend/config.py b/src/pdm/backend/config.py
--- a/src/pdm/backend/config.py	2024-04-30 03:22:19.000000000 +0200
+++ b/src/pdm/backend/config.py	2024-04-30 11:51:24.833806627 +0200
@@ -6,8 +6,8 @@
 from pathlib import Path
 from typing import TYPE_CHECKING, Any, TypeVar
 
-from pdm.backend._vendor import tomli_w
-from pdm.backend._vendor.pyproject_metadata import ConfigurationError, StandardMetadata
+import tomli_w
+from pyproject_metadata import ConfigurationError, StandardMetadata
 from pdm.backend.exceptions import ConfigError, ValidationError
 from pdm.backend.structures import Table
 from pdm.backend.utils import find_packages_iter
@@ -15,7 +15,7 @@
 if sys.version_info >= (3, 11):
     import tomllib
 else:
-    import pdm.backend._vendor.tomli as tomllib
+    import tomli as tomllib
 
 T = TypeVar("T")
 
diff -ruN a/src/pdm/backend/editable.py b/src/pdm/backend/editable.py
--- a/src/pdm/backend/editable.py	2024-04-30 03:22:19.000000000 +0200
+++ b/src/pdm/backend/editable.py	2024-04-30 11:48:17.032514926 +0200
@@ -6,7 +6,7 @@
 
 from editables import EditableProject
 
-from pdm.backend._vendor.packaging.utils import canonicalize_name
+from packaging.utils import canonicalize_name
 from pdm.backend.exceptions import ConfigError, PDMWarning
 from pdm.backend.hooks.base import Context
 from pdm.backend.utils import to_filename
diff -ruN a/src/pdm/backend/hooks/version/scm.py b/src/pdm/backend/hooks/version/scm.py
--- a/src/pdm/backend/hooks/version/scm.py	2024-04-30 03:22:19.000000000 +0200
+++ b/src/pdm/backend/hooks/version/scm.py	2024-04-30 11:48:38.086000675 +0200
@@ -16,7 +16,7 @@
 from pathlib import Path
 from typing import TYPE_CHECKING, Callable, NamedTuple
 
-from pdm.backend._vendor.packaging.version import Version
+from packaging.version import Version
 
 if TYPE_CHECKING:
     from _typeshed import StrPath
diff -ruN a/src/pdm/backend/intree.py b/src/pdm/backend/intree.py
--- a/src/pdm/backend/intree.py	2024-04-30 03:22:19.000000000 +0200
+++ b/src/pdm/backend/intree.py	2024-04-30 11:50:06.463285128 +0200
@@ -16,7 +16,7 @@
 if sys.version_info >= (3, 11):
     import tomllib
 else:
-    import pdm.backend._vendor.tomli as tomllib
+    import tomli as tomllib
 
 
 def get_requires_for_build_wheel(
diff -ruN a/src/pdm/backend/sdist.py b/src/pdm/backend/sdist.py
--- a/src/pdm/backend/sdist.py	2024-04-30 03:22:19.000000000 +0200
+++ b/src/pdm/backend/sdist.py	2024-04-30 11:50:30.170111969 +0200
@@ -8,7 +8,7 @@
 from posixpath import join as pjoin
 from typing import Iterable
 
-from pdm.backend._vendor.packaging.utils import canonicalize_name
+from packaging.utils import canonicalize_name
 from pdm.backend.base import Builder
 from pdm.backend.hooks import Context
 from pdm.backend.utils import normalize_file_permissions, safe_version, to_filename
diff -ruN a/src/pdm/backend/utils.py b/src/pdm/backend/utils.py
--- a/src/pdm/backend/utils.py	2024-04-30 03:22:19.000000000 +0200
+++ b/src/pdm/backend/utils.py	2024-04-30 11:50:46.970224176 +0200
@@ -14,9 +14,9 @@
 from pathlib import Path
 from typing import Any, Callable, Generator, Iterable, Match
 
-from pdm.backend._vendor.packaging.markers import Marker
-from pdm.backend._vendor.packaging.requirements import Requirement
-from pdm.backend._vendor.packaging.version import InvalidVersion, Version
+from packaging.markers import Marker
+from packaging.requirements import Requirement
+from packaging.version import InvalidVersion, Version
 from pdm.backend.exceptions import ConfigError
 
 
diff -ruN a/src/pdm/backend/wheel.py b/src/pdm/backend/wheel.py
--- a/src/pdm/backend/wheel.py	2024-04-30 03:22:19.000000000 +0200
+++ b/src/pdm/backend/wheel.py	2024-04-30 11:51:39.970571490 +0200
@@ -15,9 +15,9 @@
 from pathlib import Path
 from typing import IO, Any, Iterable, Mapping, NamedTuple, cast
 
-from pdm.backend._vendor.packaging import tags
-from pdm.backend._vendor.packaging.specifiers import SpecifierSet
-from pdm.backend._vendor.packaging.utils import _build_tag_regex, canonicalize_name
+from packaging import tags
+from packaging.specifiers import SpecifierSet
+from packaging.utils import _build_tag_regex, canonicalize_name
 from pdm.backend.base import Builder
 from pdm.backend.hooks import Context
 from pdm.backend.hooks.setuptools import SetuptoolsBuildHook