diff --git a/src/gentropy/dataset/l2g_feature_matrix.py b/src/gentropy/dataset/l2g_feature_matrix.py
index 4c611e3da..7ef526704 100644
--- a/src/gentropy/dataset/l2g_feature_matrix.py
+++ b/src/gentropy/dataset/l2g_feature_matrix.py
@@ -108,6 +108,88 @@ def get_schema(cls: type[L2GFeatureMatrix]) -> StructType:
         """
         return parse_spark_schema("l2g_feature_matrix.json")
 
+    def merge_features_in_efo(
+        self: L2GFeatureMatrix,
+        features: list[str],
+        credible_set: StudyLocus,
+        study_index: StudyIndex,
+        max_distance: int = 500000,
+    ) -> L2GFeatureMatrix:
+        """Merge studyLocusId-to-geneId pairings in the feature matrix, filling in missing features.
+
+        Args:
+            features (list[str]): List of features to merge
+            credible_set (StudyLocus): Credible set dataset
+            study_index (StudyIndex): Study index dataset
+            max_distance (int): Maximum allowed base pair distance for grouping variants. Default is 500,000.
+
+        Returns:
+            L2GFeatureMatrix: L2G feature matrix dataset
+        """
+        from pyspark.sql import functions as f
+        from pyspark.sql.window import Window
+
+        efo_df = (
+            credible_set.df.join(study_index.df, on="studyId", how="inner").select(
+                "studyId",
+                "studyLocusId",
+                "variantId",
+                f.explode(study_index.df["traitFromSourceMappedIds"]).alias(
+                    "efo_terms"
+                ),
+            )
+        ).join(
+            self._df,
+            on="studyLocusId",
+            how="inner",
+        )
+
+        efo_df = efo_df.withColumn(
+            "chromosome", f.split(f.col("variantId"), "_").getItem(0)
+        )
+        efo_df = efo_df.withColumn(
+            "position", f.split(f.col("variantId"), "_").getItem(1).cast("long")
+        )
+
+        window_spec = Window.partitionBy("efo_terms", "geneId", "chromosome").orderBy(
+            "position"
+        )
+
+        efo_df = efo_df.withColumn(
+            "position_diff", f.col("position") - f.lag("position", 1).over(window_spec)
+        )
+        efo_df = efo_df.withColumn(
+            "group",
+            f.sum(f.when(f.col("position_diff") > max_distance, 1).otherwise(0)).over(
+                window_spec
+            ),
+        )
+
+        max_df = efo_df.groupBy("efo_terms", "geneId", "group").agg(
+            *[f.max(col).alias(f"{col}_max") for col in features]
+        )
+
+        imputed_df = efo_df.join(
+            max_df, on=["efo_terms", "geneId", "group"], how="left"
+        )
+
+        for col in features:
+            imputed_df = imputed_df.withColumn(col, f.col(f"{col}_max")).drop(
+                f"{col}_max"
+            )
+
+        self.df = imputed_df.drop(
+            "efo_terms",
+            "studyId",
+            "chromosome",
+            "position",
+            "position_diff",
+            "group",
+            "variantId",
+        ).distinct()
+
+        return self
+
     def calculate_feature_missingness_rate(
         self: L2GFeatureMatrix,
     ) -> dict[str, float]:
diff --git a/src/gentropy/dataset/l2g_gold_standard.py b/src/gentropy/dataset/l2g_gold_standard.py
index 5bc48413c..d2bcc77b7 100644
--- a/src/gentropy/dataset/l2g_gold_standard.py
+++ b/src/gentropy/dataset/l2g_gold_standard.py
@@ -1,4 +1,5 @@
 """L2G gold standard dataset."""
+
 from __future__ import annotations
 
 from dataclasses import dataclass
@@ -56,6 +57,7 @@ def from_otg_curation(
             OpenTargetsL2GGoldStandard.as_l2g_gold_standard(gold_standard_curation, v2g)
             # .filter_unique_associations(study_locus_overlap)
             .remove_false_negatives(interactions_df)
+            .balance_classes()
         )
 
     @classmethod
@@ -197,3 +199,31 @@ def remove_false_negatives(
             .distinct()
         )
         return L2GGoldStandard(_df=df, _schema=self.get_schema())
+
+    def balance_classes(
+        self: L2GGoldStandard, imbalance_ratio: float = 2.0
+    ) -> L2GGoldStandard:
+        """Balances the classes of the gold standard dataset.
+
+        Args:
+            imbalance_ratio (float): maximum ratio of negative to positive samples
+
+        Returns:
+            L2GGoldStandard: A balanced gold standard dataset.
+        """
+        positive_df = self.df.filter(f.col("goldStandardSet") == self.GS_POSITIVE_LABEL)
+        negative_df = self.df.filter(f.col("goldStandardSet") == self.GS_NEGATIVE_LABEL)
+
+        negative_sample_fraction = min(
+            (positive_df.count() * imbalance_ratio / negative_df.count()), 1.0
+        )
+
+        negative_sample = negative_df.sample(
+            withReplacement=False,
+            fraction=negative_sample_fraction,
+            seed=42,
+        )
+
+        return L2GGoldStandard(
+            _df=positive_df.union(negative_sample), _schema=self.get_schema()
+        )