diff --git a/src/metakb/transformers/base.py b/src/metakb/transformers/base.py
index 163cf4a5..738de3ff 100644
--- a/src/metakb/transformers/base.py
+++ b/src/metakb/transformers/base.py
@@ -7,7 +7,7 @@
 from abc import ABC, abstractmethod
 from enum import Enum
 from pathlib import Path
-from typing import ClassVar
+from typing import ClassVar, TypeVar
 
 from disease.schemas import (
     SYSTEM_URI_TO_NAMESPACE as DISEASE_SYSTEM_URI_TO_NAMESPACE,
@@ -55,6 +55,8 @@
     NormalizedGene: "gene",
 }
 
+_CacheType = TypeVar("_CacheType", bound="_TransformedRecordsCache")
+
 
 def _sanitize_name(name: str) -> str:
     """Trim leading and trailing whitespace and replace whitespace characters with
@@ -289,7 +291,7 @@ def __init__(
         :param Optional[Path] harvester_path: Path to previously harvested data
         :param ViccNormalizers normalizers: normalizer collection instance
         """
-        self._cache: _TransformedRecordsCache
+        self._cache = self._create_cache()
         self.name = self.__class__.__name__.lower().split("transformer")[0]
         self.data_dir = data_dir / self.name
         self.harvester_path = harvester_path
@@ -308,6 +310,10 @@ async def transform(self, harvested_data: _HarvestedData) -> None:
         :param harvested_data: Source harvested data
         """
 
+    @abstractmethod
+    def _create_cache() -> _CacheType:
+        """Create cache for transformed records"""
+
     def extract_harvested_data(self) -> _HarvestedData:
         """Get harvested data from file.
 
diff --git a/src/metakb/transformers/civic.py b/src/metakb/transformers/civic.py
index f4d8bbe8..088cae0b 100644
--- a/src/metakb/transformers/civic.py
+++ b/src/metakb/transformers/civic.py
@@ -143,7 +143,7 @@ class _VariationCache(BaseModel):
     aliases: list[Extension] | None = None
     coordinates: dict | None = None
     members: list[Variation] | None = None
-    extensions: list[Extension] = []
+    extensions: list[Extension] | None = None
 
 
 class SourcePrefix(str, Enum):
@@ -192,7 +192,11 @@ def __init__(
         self.processed_data.methods = [
             self.methods_mapping[MethodId.CIVIC_EID_SOP.value]
         ]
-        self._cache = _CivicTransformedCache()
+        self._cache = self._create_cache()
+
+    def _create_cache(self) -> _CivicTransformedCache:
+        """Create cache for transformed records"""
+        return _CivicTransformedCache()
 
     @staticmethod
     def _mp_to_variant_mapping(molecular_profiles: list[dict]) -> tuple[list, dict]:
@@ -611,7 +615,7 @@ def _is_supported_variant_query(variant_name: str, variant_id: int) -> bool:
 
         return True
 
-    async def _get_variation_members(self, variant: dict) -> list[Variation] | None:
+    async def _get_variation_members(self, variant: dict) -> list[Variation]:
         """Get members field for variation object. This is the related variant concepts.
 
         :param variant: CIViC Variant record
@@ -701,7 +705,7 @@ async def _add_variations(self, variants: list[dict]) -> None:
                     label="_".join(vt["name"].lower().split()),
                 )
                 for vt in variant["variant_types"]
-                if vt and vt["url"]
+                if vt and vt["url"]  # system is required
             ]
 
             # Get mappings
diff --git a/src/metakb/transformers/moa.py b/src/metakb/transformers/moa.py
index 80df3c0e..f40b19e8 100644
--- a/src/metakb/transformers/moa.py
+++ b/src/metakb/transformers/moa.py
@@ -76,7 +76,11 @@ def __init__(
         self.processed_data.methods = [
             self.methods_mapping[MethodId.MOA_ASSERTION_BIORXIV.value]
         ]
-        self._cache = _MoaTransformedCache()
+        self._cache = self._create_cache()
+
+    def _create_cache(self) -> _MoaTransformedCache:
+        """Create cache for transformed records"""
+        return _MoaTransformedCache()
 
     async def transform(self, harvested_data: MoaHarvestedData) -> None:
         """Transform MOA harvested JSON to common data model. Will store transformed
@@ -223,10 +227,11 @@ async def _add_categorical_variants(self, variants: list[dict]) -> None:
             moa_variation = None
             gene = variant.get("gene") or variant.get("gene1")
             moa_gene = self._cache.genes[_sanitize_name(gene)]
+            protein_change = variant.get("protein_change")
             constraints = None
             extensions = []
 
-            if "rearrangement_type" in variant:
+            if "rearrangement_type" in variant or not protein_change:
                 logger.debug(
                     "Variation Normalizer does not support %s: %s",
                     moa_variant_id,
@@ -237,37 +242,24 @@ async def _add_categorical_variants(self, variants: list[dict]) -> None:
                 # Form query and run through variation-normalizer
                 # For now, the normalizer only support amino acid substitution
                 vrs_variation = None
-                if variant.get("protein_change"):
-                    gene = moa_gene.label
-                    query = f"{gene} {variant['protein_change'][2:]}"
-                    vrs_variation = await self.vicc_normalizers.normalize_variation(
-                        [query]
-                    )
-
-                    if not vrs_variation:
-                        logger.debug(
-                            "Variation Normalizer unable to normalize: moa.variant: %s using query: %s",
-                            variant_id,
-                            query,
-                        )
-                        extensions.append(self._get_vicc_normalizer_failure_ext())
-                    else:
-                        # Create VRS Variation object
-                        params = vrs_variation.model_dump(exclude_none=True)
-                        moa_variant_id = f"moa.variant:{variant_id}"
-                        params["id"] = vrs_variation.id
-                        moa_variation = Variation(**params)
-                        constraints = [
-                            DefiningAlleleConstraint(allele=moa_variation.root)
-                        ]
+                gene = moa_gene.label
+                query = f"{gene} {protein_change[2:]}"
+                vrs_variation = await self.vicc_normalizers.normalize_variation([query])
 
-                else:
+                if not vrs_variation:
                     logger.debug(
-                        "Variation Normalizer does not support %s: %s",
-                        moa_variant_id,
-                        feature,
+                        "Variation Normalizer unable to normalize: moa.variant: %s using query: %s",
+                        variant_id,
+                        query,
                     )
                     extensions.append(self._get_vicc_normalizer_failure_ext())
+                else:
+                    # Create VRS Variation object
+                    params = vrs_variation.model_dump(exclude_none=True)
+                    moa_variant_id = f"moa.variant:{variant_id}"
+                    params["id"] = vrs_variation.id
+                    moa_variation = Variation(**params)
+                    constraints = [DefiningAlleleConstraint(allele=moa_variation.root)]
 
             # Add MOA representative coordinate data to extensions
             coordinates_keys = [