diff --git a/src/crested/tl/_crested.py b/src/crested/tl/_crested.py
index 986beb9..8090e04 100644
--- a/src/crested/tl/_crested.py
+++ b/src/crested/tl/_crested.py
@@ -10,13 +10,11 @@
 from anndata import AnnData
 from loguru import logger
 from tqdm import tqdm
-from typing import Callable, Any
 
 from crested._logging import log_and_raise
 from crested.tl import TaskConfig
 from crested.tl._utils import (
     _weighted_difference,
-    EnhancerOptimizer,
     generate_motif_insertions,
     generate_mutagenesis,
     hot_encoding_to_sequence,
@@ -1138,58 +1136,47 @@ def enhancer_design_motif_implementation(
 
     def enhancer_design_in_silico_evolution(
         self,
+        target_class: str,
         n_mutations: int,
         n_sequences: int,
-        target_class: str | None = None,
         return_intermediate: bool = False,
+        class_penalty_weights: np.ndarray | None = None,
         no_mutation_flanks: tuple | None = None,
         target_len: int | None = None,
-        enhancer_optimizer: EnhancerOptimizer | None = None,
-        **kwargs: dict[str, Any]
     ) -> tuple[list[dict], list] | list:
         """
         Create synthetic enhancers for a specified class using in silico evolution (ISE).
 
         Parameters
         ----------
+        target_class
+            Class name for which the enhancers will be designed for.
         n_mutations
             Number of mutations per sequence
         n_sequences
             Number of enhancers to design
-        target_class
-            Class name for which the enhancers will be designed for. If this value is set to None a custom target can be
-            defined using kwargs.
         return_intermediate
             If True, returns a dictionary with predictions and changes made in intermediate steps for selected
             sequences
+        class_penalty_weights
+            Array with a value per class, determining the penalty weight for that class to be used in scoring
+            function for sequence selection.
         no_mutation_flanks
             A tuple of integers which determine the regions in each flank to not do implementations.
         target_len
             Length of the area in the center of the sequence to make implementations, ignored if no_mutation_flanks
             is supplied.
-        enhancer_optimizer
-            An instance of EnhancerOptimizer, defining how sequences should be optimized.
-            If None, a default EnhancerOptimizer will be initialized using `_weighted_difference`
-            as optimization function.
-        kwargs
-            Keyword arguments that will be passed to the `get_best` function of the EnhancerOptimizer
 
         Returns
         -------
         A list of designed sequences and if return_intermediate is True a list of dictionaries of intermediate
         mutations and predictions
         """
-        if target_class is not None:
-            self._check_contribution_scores_params([target_class])
-
-            all_class_names = list(self.anndatamodule.adata.obs_names)
+        self._check_contribution_scores_params([target_class])
 
-            target = all_class_names.index(target_class)
+        all_class_names = list(self.anndatamodule.adata.obs_names)
 
-        if enhancer_optimizer is None:
-            enhancer_optimizer = EnhancerOptimizer(
-                optimize_func = _weighted_difference
-            )
+        target = all_class_names.index(target_class)
 
         # get input sequence length of the model
         seq_len = (
@@ -1250,12 +1237,11 @@ def enhancer_design_in_silico_evolution(
                 mutagenesis_predictions = self.model.predict(mutagenesis)
 
                 # determine the best mutation
-
-                best_mutation = enhancer_optimizer.get_best(
-                    mutated_predictions = mutagenesis_predictions,
-                    original_prediction = current_prediction,
-                    target = target,
-                    **kwargs
+                best_mutation = _weighted_difference(
+                    mutagenesis_predictions,
+                    current_prediction,
+                    target,
+                    class_penalty_weights,
                 )
 
                 sequence_onehot = mutagenesis[best_mutation : best_mutation + 1]
diff --git a/src/crested/tl/_utils.py b/src/crested/tl/_utils.py
index 79ffc57..e6fbd06 100644
--- a/src/crested/tl/_utils.py
+++ b/src/crested/tl/_utils.py
@@ -1,7 +1,5 @@
 from __future__ import annotations
 
-from typing import Any, Callable
-
 import numpy as np
 
 
@@ -94,32 +92,9 @@ def generate_motif_insertions(x, motif, flanks=(0, 0), masked_locations=None):
 
     return np.concatenate(x_mut, axis=0), insertion_locations
 
-class EnhancerOptimizer:
-    def __init__(
-            self,
-            optimize_func: Callable[..., np.intp]
-            ) -> None:
-        self.optimize_func = optimize_func
-
-    def get_best(
-        self,
-        mutated_predictions: np.ndarray,
-        original_prediction: np.ndarray,
-        target: int | list[int],
-        **kwargs: dict[str, Any]
-    ) -> np.intp:
-        return self.optimize_func(
-            mutated_predictions,
-            original_prediction,
-            target,
-            **kwargs
-        )
 
 def _weighted_difference(
-    mutated_predictions: np.ndarray,
-    original_prediction: np.ndarray,
-    target: int,
-    class_penalty_weights: np.ndarray | None = None
+    mutated_predictions, original_prediction, target, class_penalty_weights=None
 ):
     n_classes = original_prediction.shape[1]
     penalty_factor = 1 / n_classes